Merge pull request #296284 from ExpidusOS/feat/llvm-18

llvmPackages_18: init
2024-03-28 00:58:16 -07:00 · 2024-03-28 00:58:16 -07:00 · 6fb20db673
commit 6fb20db673
parent 95d5f0bb42 0df1dae88b
42 changed files with 2037 additions and 171 deletions
--- a/maintainers/team-list.nix
+++ b/maintainers/team-list.nix
@ -560,6 +560,7 @@ with lib.maintainers; {
      lovek323
      qyliss
      raitobezarius
+      RossComputerGuy
      rrbutani
      sternenseemann
    ];
--- a/pkgs/development/compilers/llvm/18/clang/default.nix
+++ b/pkgs/development/compilers/llvm/18/clang/default.nix
@ -0,0 +1,139 @@
+{ lib, stdenv, llvm_meta
+, monorepoSrc, runCommand
+, substituteAll, cmake, ninja, libxml2, libllvm, version, python3
+, buildLlvmTools
+, fixDarwinDylibNames
+, enableManpages ? false
+}:
+
+let
+  self = stdenv.mkDerivation (finalAttrs: rec {
+    pname = "clang";
+    inherit version;
+
+    src = runCommand "${pname}-src-${version}" {} ''
+      mkdir -p "$out"
+      cp -r ${monorepoSrc}/cmake "$out"
+      cp -r ${monorepoSrc}/${pname} "$out"
+      cp -r ${monorepoSrc}/clang-tools-extra "$out"
+    '';
+
+    sourceRoot = "${src.name}/${pname}";
+
+    nativeBuildInputs = [ cmake ninja python3 ]
+      ++ lib.optional (lib.versionAtLeast version "18" && enableManpages) python3.pkgs.myst-parser
+      ++ lib.optional enableManpages python3.pkgs.sphinx
+      ++ lib.optional stdenv.hostPlatform.isDarwin fixDarwinDylibNames;
+
+    buildInputs = [ libxml2 libllvm ];
+
+    cmakeFlags = [
+      "-DCLANG_INSTALL_PACKAGE_DIR=${placeholder "dev"}/lib/cmake/clang"
+      "-DCLANGD_BUILD_XPC=OFF"
+      "-DLLVM_ENABLE_RTTI=ON"
+      "-DLLVM_INCLUDE_TESTS=OFF"
+    ] ++ lib.optionals enableManpages [
+      "-DCLANG_INCLUDE_DOCS=ON"
+      "-DLLVM_ENABLE_SPHINX=ON"
+      "-DSPHINX_OUTPUT_MAN=ON"
+      "-DSPHINX_OUTPUT_HTML=OFF"
+      "-DSPHINX_WARNINGS_AS_ERRORS=OFF"
+    ] ++ lib.optionals (!stdenv.buildPlatform.canExecute stdenv.hostPlatform) [
+      "-DLLVM_TABLEGEN_EXE=${buildLlvmTools.llvm}/bin/llvm-tblgen"
+      "-DCLANG_TABLEGEN=${buildLlvmTools.libclang.dev}/bin/clang-tblgen"
+      # Added in LLVM15:
+      # `clang-tidy-confusable-chars-gen`: https://github.com/llvm/llvm-project/commit/c3574ef739fbfcc59d405985a3a4fa6f4619ecdb
+      # `clang-pseudo-gen`: https://github.com/llvm/llvm-project/commit/cd2292ef824591cc34cc299910a3098545c840c7
+      "-DCLANG_TIDY_CONFUSABLE_CHARS_GEN=${buildLlvmTools.libclang.dev}/bin/clang-tidy-confusable-chars-gen"
+      "-DCLANG_PSEUDO_GEN=${buildLlvmTools.libclang.dev}/bin/clang-pseudo-gen"
+    ];
+
+    patches = [
+      ./purity.patch
+      # https://reviews.llvm.org/D51899
+      ./gnu-install-dirs.patch
+      ../../common/clang/add-nostdlibinc-flag.patch
+      (substituteAll {
+        src = ../../common/clang/clang-at-least-16-LLVMgold-path.patch;
+       libllvmLibdir = "${libllvm.lib}/lib";
+      })
+    ];
+
+    postPatch = ''
+      (cd tools && ln -s ../../clang-tools-extra extra)
+    '' + lib.optionalString stdenv.hostPlatform.isMusl ''
+      sed -i -e 's/lgcc_s/lgcc_eh/' lib/Driver/ToolChains/*.cpp
+    '';
+
+    outputs = [ "out" "lib" "dev" "python" ];
+
+    postInstall = ''
+      ln -sv $out/bin/clang $out/bin/cpp
+
+      # Move libclang to 'lib' output
+      moveToOutput "lib/libclang.*" "$lib"
+      moveToOutput "lib/libclang-cpp.*" "$lib"
+      substituteInPlace $dev/lib/cmake/clang/ClangTargets-release.cmake \
+          --replace "\''${_IMPORT_PREFIX}/lib/libclang." "$lib/lib/libclang." \
+          --replace "\''${_IMPORT_PREFIX}/lib/libclang-cpp." "$lib/lib/libclang-cpp."
+
+      mkdir -p $python/bin $python/share/clang/
+      mv $out/bin/{git-clang-format,scan-view} $python/bin
+      if [ -e $out/bin/set-xcode-analyzer ]; then
+        mv $out/bin/set-xcode-analyzer $python/bin
+      fi
+      mv $out/share/clang/*.py $python/share/clang
+      rm $out/bin/c-index-test
+      patchShebangs $python/bin
+
+      mkdir -p $dev/bin
+      cp bin/{clang-tblgen,clang-tidy-confusable-chars-gen,clang-pseudo-gen} $dev/bin
+    '';
+
+    passthru = {
+      inherit libllvm;
+      isClang = true;
+      hardeningUnsupportedFlags = [
+        "fortify3"
+      ];
+      hardeningUnsupportedFlagsByTargetPlatform = targetPlatform:
+        lib.optional (!(targetPlatform.isx86_64 || targetPlatform.isAarch64)) "zerocallusedregs"
+        ++ (finalAttrs.passthru.hardeningUnsupportedFlags or []);
+    };
+
+    meta = llvm_meta // {
+      homepage = "https://clang.llvm.org/";
+      description = "A C language family frontend for LLVM";
+      longDescription = ''
+        The Clang project provides a language front-end and tooling
+        infrastructure for languages in the C language family (C, C++, Objective
+        C/C++, OpenCL, CUDA, and RenderScript) for the LLVM project.
+        It aims to deliver amazingly fast compiles, extremely useful error and
+        warning messages and to provide a platform for building great source
+        level tools. The Clang Static Analyzer and clang-tidy are tools that
+        automatically find bugs in your code, and are great examples of the sort
+        of tools that can be built using the Clang frontend as a library to
+        parse C/C++ code.
+      '';
+      mainProgram = "clang";
+    };
+  } // lib.optionalAttrs enableManpages {
+    pname = "clang-manpages";
+
+    ninjaFlags = [ "docs-clang-man" ];
+
+    installPhase = ''
+      mkdir -p $out/share/man/man1
+      # Manually install clang manpage
+      cp docs/man/*.1 $out/share/man/man1/
+    '';
+
+    outputs = [ "out" ];
+
+    doCheck = false;
+
+    meta = llvm_meta // {
+      description = "man page for Clang ${version}";
+    };
+  });
+in self
--- a/pkgs/development/compilers/llvm/18/clang/gnu-install-dirs.patch
+++ b/pkgs/development/compilers/llvm/18/clang/gnu-install-dirs.patch
@ -0,0 +1,71 @@
+diff --git a/cmake/modules/AddClang.cmake b/cmake/modules/AddClang.cmake
+index 75b0080f6715..c895b884cd27 100644
+--- a/cmake/modules/AddClang.cmake
+++ b/cmake/modules/AddClang.cmake
+@@ -119,8 +119,8 @@ macro(add_clang_library name)
+         install(TARGETS ${lib}
+           COMPONENT ${lib}
+           ${export_to_clangtargets}
+-          LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+-          ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+          LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}"
+          ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}"
+           RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
+ 
+         if (NOT LLVM_ENABLE_IDE)
+diff --git a/lib/Headers/CMakeLists.txt b/lib/Headers/CMakeLists.txt
+index f2b0c5cddcbb..52f37fc368ce 100644
+--- a/lib/Headers/CMakeLists.txt
+++ b/lib/Headers/CMakeLists.txt
+@@ -473,6 +473,7 @@ add_header_target("windows-resource-headers" ${windows_only_files})
+ add_header_target("utility-resource-headers" ${utility_files})
+ 
+ get_clang_resource_dir(header_install_dir SUBDIR include)
+set(header_install_dir ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/clang/${CLANG_VERSION_MAJOR}/include)
+ 
+ #############################################################
+ # Install rules for the catch-all clang-resource-headers target
+diff --git a/tools/libclang/CMakeLists.txt b/tools/libclang/CMakeLists.txt
+index 4f23065a2472..6a0f55991e24 100644
+--- a/tools/libclang/CMakeLists.txt
+++ b/tools/libclang/CMakeLists.txt
+@@ -234,7 +234,7 @@ foreach(PythonVersion ${CLANG_PYTHON_BINDINGS_VERSIONS})
+           COMPONENT
+             libclang-python-bindings
+           DESTINATION
+-            "lib${LLVM_LIBDIR_SUFFIX}/python${PythonVersion}/site-packages")
+            "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/python${PythonVersion}/site-packages")
+ endforeach()
+ if(NOT LLVM_ENABLE_IDE)
+   add_custom_target(libclang-python-bindings)
+diff --git a/tools/scan-build-py/CMakeLists.txt b/tools/scan-build-py/CMakeLists.txt
+index 3aca22c0b0a8..3115353e3fe3 100644
+--- a/tools/scan-build-py/CMakeLists.txt
+++ b/tools/scan-build-py/CMakeLists.txt
+@@ -88,7 +88,7 @@ foreach(lib ${LibScanbuild})
+                      DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/lib/libscanbuild/${lib})
+   list(APPEND Depends ${CMAKE_BINARY_DIR}/lib/libscanbuild/${lib})
+   install(FILES lib/libscanbuild/${lib}
+-          DESTINATION lib${CLANG_LIBDIR_SUFFIX}/libscanbuild
+          DESTINATION "${CMAKE_INSTALL_LIBDIR}/libscanbuild"
+           COMPONENT scan-build-py)
+ endforeach()
+ 
+@@ -106,7 +106,7 @@ foreach(resource ${LibScanbuildResources})
+                      DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/lib/libscanbuild/resources/${resource})
+   list(APPEND Depends ${CMAKE_BINARY_DIR}/lib/libscanbuild/resources/${resource})
+   install(FILES lib/libscanbuild/resources/${resource}
+-          DESTINATION lib${CLANG_LIBDIR_SUFFIX}/libscanbuild/resources
+          DESTINATION "${CMAKE_INSTALL_LIBDIR}/libscanbuild/resources"
+           COMPONENT scan-build-py)
+ endforeach()
+ 
+@@ -122,7 +122,7 @@ foreach(lib ${LibEar})
+                      DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/lib/libear/${lib})
+   list(APPEND Depends ${CMAKE_BINARY_DIR}/lib/libear/${lib})
+   install(FILES lib/libear/${lib}
+-          DESTINATION lib${CLANG_LIBDIR_SUFFIX}/libear
+          DESTINATION "${CMAKE_INSTALL_LIBDIR}/libear"
+           COMPONENT scan-build-py)
+ endforeach()
+ 
--- a/pkgs/development/compilers/llvm/18/clang/purity.patch
+++ b/pkgs/development/compilers/llvm/18/clang/purity.patch
@ -0,0 +1,25 @@
+From 4add81bba40dcec62c4ea4481be8e35ac53e89d8 Mon Sep 17 00:00:00 2001
+From: Will Dietz <w@wdtz.org>
+Date: Thu, 18 May 2017 11:56:12 -0500
+Subject: [PATCH] "purity" patch for 5.0
+
+---
+ lib/Driver/ToolChains/Gnu.cpp | 3 ---
+ 1 file changed, 3 deletions(-)
+
+diff --git a/lib/Driver/ToolChains/Gnu.cpp b/lib/Driver/ToolChains/Gnu.cpp
+index fe3c0191bb..c6a482bece 100644
+--- a/lib/Driver/ToolChains/Gnu.cpp
+++ b/lib/Driver/ToolChains/Gnu.cpp
+@@ -446,9 +446,6 @@ void tools::gnutools::Linker::ConstructJob(Compilation &C, const JobAction &JA,
+                            ToolChain.isPIEDefault(Args));
+       if (IsPIE)
+         CmdArgs.push_back("-pie");
+-      CmdArgs.push_back("-dynamic-linker");
+-      CmdArgs.push_back(Args.MakeArgString(Twine(D.DyldPrefix) +
+-                                           ToolChain.getDynamicLinker(Args)));
+     }
+   }
+ 
+-- 
+2.11.0
--- a/pkgs/development/compilers/llvm/18/compiler-rt/X86-support-extension.patch
+++ b/pkgs/development/compilers/llvm/18/compiler-rt/X86-support-extension.patch
@ -0,0 +1,21 @@
+diff --git a/lib/builtins/CMakeLists.txt b/lib/builtins/CMakeLists.txt
+index 3a66dd9c3fb..7efc85d9f9f 100644
+--- a/lib/builtins/CMakeLists.txt
+++ b/lib/builtins/CMakeLists.txt
+@@ -348,4 +348,8 @@ if (NOT MSVC)
+ 
+  set(i486_SOURCES ${i386_SOURCES})
+  set(i586_SOURCES ${i386_SOURCES})
+  set(i686_SOURCES ${i386_SOURCES})
+
+   if (WIN32)
+     set(i386_SOURCES
+       ${i386_SOURCES}
+@@ -723,6 +723,7 @@ else ()
+   endif()
+ 
+   foreach (arch ${BUILTIN_SUPPORTED_ARCH})
+      message("arch: ${arch}")
+     if (CAN_TARGET_${arch})
+       # For ARM archs, exclude any VFP builtins if VFP is not supported
+       if (${arch} MATCHES "^(arm|armhf|armv7|armv7s|armv7k|armv7m|armv7em)$")
--- a/pkgs/development/compilers/llvm/18/compiler-rt/darwin-targetconditionals.patch
+++ b/pkgs/development/compilers/llvm/18/compiler-rt/darwin-targetconditionals.patch
@ -0,0 +1,71 @@
+diff --git a/lib/sanitizer_common/sanitizer_mac.cpp b/lib/sanitizer_common/sanitizer_mac.cpp
+--- a/lib/sanitizer_common/sanitizer_mac.cpp
+++ b/lib/sanitizer_common/sanitizer_mac.cpp
+@@ -613,9 +613,15 @@ HandleSignalMode GetHandleSignalMode(int signum) {
+ // Offset example:
+ // XNU 17 -- macOS 10.13 -- iOS 11 -- tvOS 11 -- watchOS 4
+ constexpr u16 GetOSMajorKernelOffset() {
+-  if (TARGET_OS_OSX) return 4;
+-  if (TARGET_OS_IOS || TARGET_OS_TV) return 6;
+-  if (TARGET_OS_WATCH) return 13;
+#if TARGET_OS_OSX
+  return 4;
+#endif
+#if TARGET_OS_IOS || TARGET_OS_TV
+  return 6;
+#endif
+#if TARGET_OS_WATCH
+  return 13;
+#endif
+ }
+ 
+ using VersStr = char[64];
+@@ -627,13 +633,13 @@ static uptr ApproximateOSVersionViaKernelVersion(VersStr vers) {
+   u16 os_major = kernel_major - offset;
+ 
+   const char *format = "%d.0";
+-  if (TARGET_OS_OSX) {
+-    if (os_major >= 16) {  // macOS 11+
+-      os_major -= 5;
+-    } else {  // macOS 10.15 and below
+-      format = "10.%d";
+-    }
+#if TARGET_OS_OSX
+  if (os_major >= 16) {  // macOS 11+
+    os_major -= 5;
+  } else {  // macOS 10.15 and below
+    format = "10.%d";
+   }
+#endif
+   return internal_snprintf(vers, sizeof(VersStr), format, os_major);
+ }
+ 
+@@ -681,15 +687,14 @@ void ParseVersion(const char *vers, u16 *major, u16 *minor) {
+ // Aligned versions example:
+ // macOS 10.15 -- iOS 13 -- tvOS 13 -- watchOS 6
+ static void MapToMacos(u16 *major, u16 *minor) {
+-  if (TARGET_OS_OSX)
+-    return;
+-
+-  if (TARGET_OS_IOS || TARGET_OS_TV)
+#if !TARGET_OS_OSX
+#if TARGET_OS_IOS || TARGET_OS_TV
+     *major += 2;
+-  else if (TARGET_OS_WATCH)
+#elif TARGET_OS_WATCH
+     *major += 9;
+-  else
+#else
+     UNREACHABLE("unsupported platform");
+#endif
+ 
+   if (*major >= 16) {  // macOS 11+
+     *major -= 5;
+@@ -697,6 +702,7 @@ static void MapToMacos(u16 *major, u16 *minor) {
+     *minor = *major;
+     *major = 10;
+   }
+#endif
+ }
+ 
+ static MacosVersion GetMacosAlignedVersionInternal() {
--- a/pkgs/development/compilers/llvm/18/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/18/compiler-rt/default.nix
@ -0,0 +1,157 @@
+{ lib, stdenv, llvm_meta, version
+, monorepoSrc, runCommand
+, cmake, ninja, python3, xcbuild, libllvm, linuxHeaders, libxcrypt
+, doFakeLibgcc ? stdenv.hostPlatform.isFreeBSD
+}:
+
+let
+
+  useLLVM = stdenv.hostPlatform.useLLVM or false;
+  bareMetal = stdenv.hostPlatform.parsed.kernel.name == "none";
+  haveLibc = stdenv.cc.libc != null;
+  isDarwinStatic = stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isStatic;
+  inherit (stdenv.hostPlatform) isMusl;
+
+  baseName = "compiler-rt";
+
+  src = runCommand "${baseName}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${baseName} "$out"
+  '';
+in
+
+stdenv.mkDerivation {
+  pname = baseName + lib.optionalString (haveLibc) "-libc";
+  inherit version;
+
+  inherit src;
+  sourceRoot = "${src.name}/${baseName}";
+
+  nativeBuildInputs = [ cmake ninja python3 libllvm.dev ]
+    ++ lib.optional stdenv.isDarwin xcbuild.xcrun;
+  buildInputs =
+    lib.optional (stdenv.hostPlatform.isLinux && stdenv.hostPlatform.isRiscV) linuxHeaders;
+
+  env.NIX_CFLAGS_COMPILE = toString ([
+    "-DSCUDO_DEFAULT_OPTIONS=DeleteSizeMismatch=0:DeallocationTypeMismatch=0"
+  ] ++ lib.optionals (!haveLibc) [
+    # The compiler got stricter about this, and there is a usellvm patch below
+    # which patches out the assert include causing an implicit definition of
+    # assert. It would be nicer to understand why compiler-rt thinks it should
+    # be able to #include <assert.h> in the first place; perhaps it's in the
+    # wrong, or perhaps there is a way to provide an assert.h.
+    "-Wno-error=implicit-function-declaration"
+  ]);
+
+  cmakeFlags = [
+    "-DCOMPILER_RT_DEFAULT_TARGET_ONLY=ON"
+    "-DCMAKE_C_COMPILER_TARGET=${stdenv.hostPlatform.config}"
+    "-DCMAKE_ASM_COMPILER_TARGET=${stdenv.hostPlatform.config}"
+  ] ++ lib.optionals (haveLibc && stdenv.hostPlatform.libc == "glibc") [
+    "-DSANITIZER_COMMON_CFLAGS=-I${libxcrypt}/include"
+  ] ++ lib.optionals (useLLVM || bareMetal || isMusl || isDarwinStatic) [
+    "-DCOMPILER_RT_BUILD_SANITIZERS=OFF"
+    "-DCOMPILER_RT_BUILD_XRAY=OFF"
+    "-DCOMPILER_RT_BUILD_LIBFUZZER=OFF"
+    "-DCOMPILER_RT_BUILD_MEMPROF=OFF"
+    "-DCOMPILER_RT_BUILD_ORC=OFF" # may be possible to build with musl if necessary
+  ] ++ lib.optionals (useLLVM || bareMetal) [
+     "-DCOMPILER_RT_BUILD_PROFILE=OFF"
+  ] ++ lib.optionals ((useLLVM && !haveLibc) || bareMetal || isDarwinStatic ) [
+    "-DCMAKE_CXX_COMPILER_WORKS=ON"
+  ] ++ lib.optionals ((useLLVM && !haveLibc) || bareMetal) [
+    "-DCMAKE_C_COMPILER_WORKS=ON"
+    "-DCOMPILER_RT_BAREMETAL_BUILD=ON"
+    "-DCMAKE_SIZEOF_VOID_P=${toString (stdenv.hostPlatform.parsed.cpu.bits / 8)}"
+  ] ++ lib.optionals (useLLVM && !haveLibc) [
+    "-DCMAKE_C_FLAGS=-nodefaultlibs"
+  ] ++ lib.optionals (useLLVM) [
+    "-DCOMPILER_RT_BUILD_BUILTINS=ON"
+    #https://stackoverflow.com/questions/53633705/cmake-the-c-compiler-is-not-able-to-compile-a-simple-test-program
+    "-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY"
+  ] ++ lib.optionals (bareMetal) [
+    "-DCOMPILER_RT_OS_DIR=baremetal"
+  ] ++ lib.optionals (stdenv.hostPlatform.isDarwin) [
+    "-DCMAKE_LIPO=${lib.getBin stdenv.cc.bintools.bintools}/bin/${stdenv.cc.targetPrefix}lipo"
+    "-DDARWIN_macosx_OVERRIDE_SDK_VERSION=ON"
+    "-DDARWIN_osx_ARCHS=${stdenv.hostPlatform.darwinArch}"
+    "-DDARWIN_osx_BUILTIN_ARCHS=${stdenv.hostPlatform.darwinArch}"
+
+    # `COMPILER_RT_DEFAULT_TARGET_ONLY` does not apply to Darwin:
+    # https://github.com/llvm/llvm-project/blob/27ef42bec80b6c010b7b3729ed0528619521a690/compiler-rt/cmake/base-config-ix.cmake#L153
+    "-DCOMPILER_RT_ENABLE_IOS=OFF"
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  patches = [
+    ./X86-support-extension.patch # Add support for i486 i586 i686 by reusing i386 config
+    # ld-wrapper dislikes `-rpath-link //nix/store`, so we normalize away the
+    # extra `/`.
+    ./normalize-var.patch
+    # See: https://github.com/NixOS/nixpkgs/pull/186575
+    ../../common/compiler-rt/darwin-plistbuddy-workaround.patch
+    # See: https://github.com/NixOS/nixpkgs/pull/194634#discussion_r999829893
+    # ../../common/compiler-rt/armv7l-15.patch
+  ];
+
+  # TSAN requires XPC on Darwin, which we have no public/free source files for. We can depend on the Apple frameworks
+  # to get it, but they're unfree. Since LLVM is rather central to the stdenv, we patch out TSAN support so that Hydra
+  # can build this. If we didn't do it, basically the entire nixpkgs on Darwin would have an unfree dependency and we'd
+  # get no binary cache for the entire platform. If you really find yourself wanting the TSAN, make this controllable by
+  # a flag and turn the flag off during the stdenv build.
+  postPatch = lib.optionalString (!stdenv.isDarwin) ''
+    substituteInPlace cmake/builtin-config-ix.cmake \
+      --replace 'set(X86 i386)' 'set(X86 i386 i486 i586 i686)'
+  '' + lib.optionalString stdenv.isDarwin ''
+    substituteInPlace cmake/config-ix.cmake \
+      --replace 'set(COMPILER_RT_HAS_TSAN TRUE)' 'set(COMPILER_RT_HAS_TSAN FALSE)'
+  '' + lib.optionalString (useLLVM && !haveLibc) ''
+    substituteInPlace lib/builtins/aarch64/sme-libc-routines.c \
+      --replace "<stdlib.h>" "<stddef.h>"
+    substituteInPlace lib/builtins/int_util.c \
+      --replace "#include <stdlib.h>" ""
+    substituteInPlace lib/builtins/clear_cache.c \
+      --replace "#include <assert.h>" ""
+    substituteInPlace lib/builtins/cpu_model${lib.optionalString (lib.versionAtLeast version "18") "/x86"}.c \
+      --replace "#include <assert.h>" ""
+  '';
+
+  # Hack around weird upsream RPATH bug
+  postInstall = lib.optionalString (stdenv.hostPlatform.isDarwin) ''
+    ln -s "$out/lib"/*/* "$out/lib"
+  '' + lib.optionalString (useLLVM && stdenv.hostPlatform.isLinux) ''
+    ln -s $out/lib/*/clang_rt.crtbegin-*.o $out/lib/crtbegin.o
+    ln -s $out/lib/*/clang_rt.crtend-*.o $out/lib/crtend.o
+    # Note the history of crt{begin,end}S in previous versions of llvm in nixpkg:
+    # The presence of crtbegin_shared has been added and removed; it's possible
+    # people have added/removed it to get it working on their platforms.
+    # Try each in turn for now.
+    ln -s $out/lib/*/clang_rt.crtbegin-*.o $out/lib/crtbeginS.o
+    ln -s $out/lib/*/clang_rt.crtend-*.o $out/lib/crtendS.o
+    ln -s $out/lib/*/clang_rt.crtbegin_shared-*.o $out/lib/crtbeginS.o
+    ln -s $out/lib/*/clang_rt.crtend_shared-*.o $out/lib/crtendS.o
+  '' + lib.optionalString doFakeLibgcc ''
+     ln -s $out/lib/freebsd/libclang_rt.builtins-*.a $out/lib/libgcc.a
+  '';
+
+  meta = llvm_meta // {
+    homepage = "https://compiler-rt.llvm.org/";
+    description = "Compiler runtime libraries";
+    longDescription = ''
+      The compiler-rt project provides highly tuned implementations of the
+      low-level code generator support routines like "__fixunsdfdi" and other
+      calls generated when a target doesn't have a short sequence of native
+      instructions to implement a core IR operation. It also provides
+      implementations of run-time libraries for dynamic testing tools such as
+      AddressSanitizer, ThreadSanitizer, MemorySanitizer, and DataFlowSanitizer.
+    '';
+    # "All of the code in the compiler-rt project is dual licensed under the MIT
+    # license and the UIUC License (a BSD-like license)":
+    license = with lib.licenses; [ mit ncsa ];
+    # compiler-rt requires a Clang stdenv on 32-bit RISC-V:
+    # https://reviews.llvm.org/D43106#1019077
+    broken = stdenv.hostPlatform.isRiscV32 && !stdenv.cc.isClang;
+  };
+}
--- a/pkgs/development/compilers/llvm/18/compiler-rt/normalize-var.patch
+++ b/pkgs/development/compilers/llvm/18/compiler-rt/normalize-var.patch
@ -0,0 +1,16 @@
+diff --git a/cmake/Modules/CompilerRTUtils.cmake b/cmake/Modules/CompilerRTUtils.cmake
+index 4c85551d7766..297d7a47c54b 100644
+--- a/cmake/Modules/CompilerRTUtils.cmake
+++ b/cmake/Modules/CompilerRTUtils.cmake
+@@ -328,8 +328,9 @@ macro(load_llvm_config)
+     endif()
+   endif()
+ 
+-  set(LLVM_LIBRARY_OUTPUT_INTDIR
+-    ${LLVM_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX})
+  get_filename_component(LLVM_LIBRARY_OUTPUT_INTDIR
+    ${LLVM_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX}
+    REALPATH)
+ 
+   set(LLVM_MAIN_SRC_DIR "${LLVM_MAIN_SRC_DIR_DEFAULT}" CACHE PATH "Path to LLVM source tree")
+   message(STATUS "LLVM_MAIN_SRC_DIR: \"${LLVM_MAIN_SRC_DIR}\"")
--- a/pkgs/development/compilers/llvm/18/default.nix
+++ b/pkgs/development/compilers/llvm/18/default.nix
@ -0,0 +1,329 @@
+{ lowPrio, newScope, pkgs, lib, stdenv, cmake, ninja
+, preLibcCrossHeaders
+, libxml2, python3, fetchFromGitHub, overrideCC, wrapCCWith, wrapBintoolsWith
+, buildLlvmTools # tools, but from the previous stage, for cross
+, targetLlvmLibraries # libraries, but from the next stage, for cross
+, targetLlvm
+# This is the default binutils, but with *this* version of LLD rather
+# than the default LLVM verion's, if LLD is the choice. We use these for
+# the `useLLVM` bootstrapping below.
+, bootBintoolsNoLibc ?
+    if stdenv.targetPlatform.linker == "lld"
+    then null
+    else pkgs.bintoolsNoLibc
+, bootBintools ?
+    if stdenv.targetPlatform.linker == "lld"
+    then null
+    else pkgs.bintools
+, darwin
+# LLVM release information; specify one of these but not both:
+, gitRelease ? null
+  # i.e.:
+  # {
+  #   version = /* i.e. "15.0.0" */;
+  #   rev = /* commit SHA */;
+  #   rev-version = /* human readable version; i.e. "unstable-2022-26-07" */;
+  #   sha256 = /* checksum for this release, can omit if specifying your own `monorepoSrc` */;
+  # }
+, officialRelease ? { version = "18.1.1"; sha256 = "sha256-qAPNvEpztJjPz+kr5KcZz4iUTErsD8iXLURKl3yZoC8="; }
+  # i.e.:
+  # {
+  #   version = /* i.e. "15.0.0" */;
+  #   candidate = /* optional; if specified, should be: "rcN" */
+  #   sha256 = /* checksum for this release, can omit if specifying your own `monorepoSrc` */;
+  # }
+# By default, we'll try to fetch a release from `github:llvm/llvm-project`
+# corresponding to the `gitRelease` or `officialRelease` specified.
+#
+# You can provide your own LLVM source by specifying this arg but then it's up
+# to you to make sure that the LLVM repo given matches the release configuration
+# specified.
+, monorepoSrc ? null
+}:
+
+assert let
+  int = a: if a then 1 else 0;
+  xor = a: b: ((builtins.bitXor (int a) (int b)) == 1);
+in
+  lib.assertMsg
+    (xor
+      (gitRelease != null)
+      (officialRelease != null))
+    ("must specify `gitRelease` or `officialRelease`" +
+      (lib.optionalString (gitRelease != null) " — not both"));
+let
+  monorepoSrc' = monorepoSrc;
+in let
+  inherit (import ../common/common-let.nix { inherit lib gitRelease officialRelease; }) releaseInfo;
+
+  inherit (releaseInfo) release_version version;
+
+  inherit (import ../common/common-let.nix { inherit lib fetchFromGitHub release_version gitRelease officialRelease monorepoSrc'; }) llvm_meta monorepoSrc;
+
+  tools = lib.makeExtensible (tools: let
+    callPackage = newScope (tools // { inherit stdenv cmake ninja libxml2 python3 release_version version monorepoSrc buildLlvmTools; });
+    major = lib.versions.major release_version;
+    mkExtraBuildCommands0 = cc: ''
+      rsrc="$out/resource-root"
+      mkdir "$rsrc"
+      ln -s "${cc.lib}/lib/clang/${major}/include" "$rsrc"
+      echo "-resource-dir=$rsrc" >> $out/nix-support/cc-cflags
+    '';
+    mkExtraBuildCommands = cc: mkExtraBuildCommands0 cc + ''
+      ln -s "${targetLlvmLibraries.compiler-rt.out}/lib" "$rsrc/lib"
+      ln -s "${targetLlvmLibraries.compiler-rt.out}/share" "$rsrc/share"
+    '';
+
+  bintoolsNoLibc' =
+    if bootBintoolsNoLibc == null
+    then tools.bintoolsNoLibc
+    else bootBintoolsNoLibc;
+  bintools' =
+    if bootBintools == null
+    then tools.bintools
+    else bootBintools;
+
+  in {
+
+    libllvm = callPackage ./llvm {
+      inherit llvm_meta;
+    };
+
+    # `llvm` historically had the binaries.  When choosing an output explicitly,
+    # we need to reintroduce `outputSpecified` to get the expected behavior e.g. of lib.get*
+    llvm = tools.libllvm;
+
+    libclang = callPackage ./clang {
+      inherit llvm_meta;
+    };
+
+    clang-unwrapped = tools.libclang;
+
+    llvm-manpages = lowPrio (tools.libllvm.override {
+      enableManpages = true;
+      python3 = pkgs.python3;  # don't use python-boot
+    });
+
+    clang-manpages = lowPrio (tools.libclang.override {
+      enableManpages = true;
+      python3 = pkgs.python3;  # don't use python-boot
+    });
+
+    lldb-manpages = lowPrio (tools.lldb.override {
+      enableManpages = true;
+      python3 = pkgs.python3;  # don't use python-boot
+    });
+
+    # pick clang appropriate for package set we are targeting
+    clang =
+      /**/ if stdenv.targetPlatform.useLLVM or false then tools.clangUseLLVM
+      else if (pkgs.targetPackages.stdenv or stdenv).cc.isGNU then tools.libstdcxxClang
+      else tools.libcxxClang;
+
+    libstdcxxClang = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      # libstdcxx is taken from gcc in an ad-hoc way in cc-wrapper.
+      libcxx = null;
+      extraPackages = [
+        targetLlvmLibraries.compiler-rt
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+    };
+
+    libcxxClang = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = targetLlvmLibraries.libcxx;
+      extraPackages = [
+        targetLlvmLibraries.compiler-rt
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+    };
+
+    lld = callPackage ./lld {
+      inherit llvm_meta;
+    };
+
+    mlir = callPackage ../common/mlir {
+      inherit llvm_meta;
+    };
+
+    lldb = callPackage ../common/lldb.nix {
+      src = callPackage ({ runCommand }: runCommand "lldb-src-${version}" {} ''
+        mkdir -p "$out"
+        cp -r ${monorepoSrc}/cmake "$out"
+        cp -r ${monorepoSrc}/lldb "$out"
+      '') { };
+      patches =
+        [
+          # FIXME: do we need this? ./procfs.patch
+          ../common/lldb/gnu-install-dirs.patch
+        ]
+        # This is a stopgap solution if/until the macOS SDK used for x86_64 is
+        # updated.
+        #
+        # The older 10.12 SDK used on x86_64 as of this writing has a `mach/machine.h`
+        # header that does not define `CPU_SUBTYPE_ARM64E` so we replace the one use
+        # of this preprocessor symbol in `lldb` with its expansion.
+        #
+        # See here for some context:
+        # https://github.com/NixOS/nixpkgs/pull/194634#issuecomment-1272129132
+        ++ lib.optional (
+          stdenv.targetPlatform.isDarwin
+            && !stdenv.targetPlatform.isAarch64
+            && (lib.versionOlder darwin.apple_sdk.sdk.version "11.0")
+        ) ./lldb/cpu_subtype_arm64e_replacement.patch;
+      inherit llvm_meta;
+    };
+
+    # Below, is the LLVM bootstrapping logic. It handles building a
+    # fully LLVM toolchain from scratch. No GCC toolchain should be
+    # pulled in. As a consequence, it is very quick to build different
+    # targets provided by LLVM and we can also build for what GCC
+    # doesn’t support like LLVM. Probably we should move to some other
+    # file.
+
+    bintools-unwrapped = callPackage ../common/bintools.nix { };
+
+    bintoolsNoLibc = wrapBintoolsWith {
+      bintools = tools.bintools-unwrapped;
+      libc = preLibcCrossHeaders;
+    };
+
+    bintools = wrapBintoolsWith {
+      bintools = tools.bintools-unwrapped;
+    };
+
+    clangUseLLVM = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = targetLlvmLibraries.libcxx;
+      bintools = bintools';
+      extraPackages = [
+        targetLlvmLibraries.compiler-rt
+      ] ++ lib.optionals (!stdenv.targetPlatform.isWasm) [
+        targetLlvmLibraries.libunwind
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+      nixSupport.cc-cflags =
+        [ "-rtlib=compiler-rt"
+          "-Wno-unused-command-line-argument"
+          "-B${targetLlvmLibraries.compiler-rt}/lib"
+        ]
+        ++ lib.optional (!stdenv.targetPlatform.isWasm) "--unwindlib=libunwind"
+        ++ lib.optional
+          (!stdenv.targetPlatform.isWasm && stdenv.targetPlatform.useLLVM or false)
+          "-lunwind"
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
+      nixSupport.cc-ldflags = lib.optionals (!stdenv.targetPlatform.isWasm) [ "-L${targetLlvmLibraries.libunwind}/lib" ];
+    };
+
+    clangNoLibcxx = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = null;
+      bintools = bintools';
+      extraPackages = [
+        targetLlvmLibraries.compiler-rt
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+      nixSupport.cc-cflags =
+        [
+          "-rtlib=compiler-rt"
+          "-B${targetLlvmLibraries.compiler-rt}/lib"
+          "-nostdlib++"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
+    };
+
+    clangNoLibc = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = null;
+      bintools = bintoolsNoLibc';
+      extraPackages = [
+        targetLlvmLibraries.compiler-rt
+      ];
+      extraBuildCommands = mkExtraBuildCommands cc;
+      nixSupport.cc-cflags =
+        [
+          "-rtlib=compiler-rt"
+          "-B${targetLlvmLibraries.compiler-rt}/lib"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
+    };
+
+    clangNoCompilerRt = wrapCCWith rec {
+      cc = tools.clang-unwrapped;
+      libcxx = null;
+      bintools = bintoolsNoLibc';
+      extraPackages = [ ];
+      extraBuildCommands = mkExtraBuildCommands0 cc;
+      nixSupport.cc-cflags =
+        [
+          "-nostartfiles"
+        ]
+        ++ lib.optional stdenv.targetPlatform.isWasm "-fno-exceptions";
+    };
+
+    clangNoCompilerRtWithLibc = wrapCCWith (rec {
+      cc = tools.clang-unwrapped;
+      libcxx = null;
+      bintools = bintools';
+      extraPackages = [ ];
+      extraBuildCommands = mkExtraBuildCommands0 cc;
+    } // lib.optionalAttrs stdenv.targetPlatform.isWasm {
+      nixSupport.cc-cflags = [ "-fno-exceptions" ];
+    });
+
+    # Has to be in tools despite mostly being a library,
+    # because we use a native helper executable from a
+    # non-cross build in cross builds.
+    libclc = callPackage ../common/libclc.nix {
+      inherit buildLlvmTools;
+    };
+  });
+
+  libraries = lib.makeExtensible (libraries: let
+    callPackage = newScope (libraries // buildLlvmTools // { inherit stdenv cmake ninja libxml2 python3 release_version version monorepoSrc; });
+  in {
+
+    compiler-rt-libc = callPackage ./compiler-rt {
+      inherit llvm_meta;
+      stdenv = if stdenv.hostPlatform.useLLVM or false || (stdenv.hostPlatform.isDarwin && stdenv.hostPlatform.isStatic)
+               then overrideCC stdenv buildLlvmTools.clangNoCompilerRtWithLibc
+               else stdenv;
+    };
+
+    compiler-rt-no-libc = callPackage ./compiler-rt {
+      inherit llvm_meta;
+      stdenv = if stdenv.hostPlatform.useLLVM or false
+               then overrideCC stdenv buildLlvmTools.clangNoCompilerRt
+               else stdenv;
+    };
+
+    # N.B. condition is safe because without useLLVM both are the same.
+    compiler-rt = if stdenv.hostPlatform.isAndroid || stdenv.hostPlatform.isDarwin
+      then libraries.compiler-rt-libc
+      else libraries.compiler-rt-no-libc;
+
+    stdenv = overrideCC stdenv buildLlvmTools.clang;
+
+    libcxxStdenv = overrideCC stdenv buildLlvmTools.libcxxClang;
+
+    # `libcxx` requires a fairly modern C++ compiler,
+    # so: we use the clang from this LLVM package set instead of the regular
+    # stdenv's compiler.
+    libcxx = callPackage ./libcxx {
+      inherit llvm_meta;
+      stdenv = overrideCC stdenv buildLlvmTools.clangNoLibcxx;
+    };
+
+    libunwind = callPackage ./libunwind {
+      inherit llvm_meta;
+      stdenv = overrideCC stdenv buildLlvmTools.clangNoLibcxx;
+    };
+
+    openmp = callPackage ./openmp {
+      inherit llvm_meta targetLlvm;
+    };
+  });
+  noExtend = extensible: lib.attrsets.removeAttrs extensible [ "extend" ];
+
+in { inherit tools libraries release_version; } // (noExtend libraries) // (noExtend tools)
--- a/pkgs/development/compilers/llvm/18/libcxx/0001-darwin-10.12-mbstate_t-fix.patch
+++ b/pkgs/development/compilers/llvm/18/libcxx/0001-darwin-10.12-mbstate_t-fix.patch
@ -0,0 +1,31 @@
+From 9c1cb26c1dd3f92d1c1177e548107d2cd3c5e616 Mon Sep 17 00:00:00 2001
+From: annalee <150648636+a-n-n-a-l-e-e@users.noreply.github.com>
+Date: Fri, 23 Feb 2024 22:58:58 +0000
+Subject: [PATCH] darwin 10.12 mbstate_t fix
+
+https://github.com/llvm/llvm-project/issues/64226
+
+removes space from
+https://github.com/macports/macports-ports/raw/acd8acb171f1658596ed1cf25da48d5b932e2d19/lang/llvm-17/files/0042-mbstate_t-not-defined.patch
+so it applies cleanly
+---
+ libcxx/include/__mbstate_t.h | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/libcxx/include/__mbstate_t.h b/libcxx/include/__mbstate_t.h
+index bfa6d61..5f51112 100644
+--- a/libcxx/include/__mbstate_t.h
+++ b/libcxx/include/__mbstate_t.h
+@@ -42,6 +42,9 @@
+ #elif __has_include(<bits/types/mbstate_t.h>)
+ #  include <bits/types/mbstate_t.h> // works on most Unixes
+ #elif __has_include(<sys/_types/_mbstate_t.h>)
+#  if __has_include(<machine/_types.h>)
+#    include <machine/_types.h>
+#  endif
+ #  include <sys/_types/_mbstate_t.h> // works on Darwin
+ #elif !defined(_LIBCPP_HAS_NO_WIDE_CHARACTERS) && __has_include_next(<wchar.h>)
+ #  include_next <wchar.h> // fall back to the C standard provider of mbstate_t
+-- 
+2.43.0
+
--- a/pkgs/development/compilers/llvm/18/libcxx/default.nix
+++ b/pkgs/development/compilers/llvm/18/libcxx/default.nix
@ -0,0 +1,130 @@
+{ lib, stdenv, llvm_meta
+, monorepoSrc, runCommand
+, cmake, lndir, ninja, python3, fixDarwinDylibNames, version
+, cxxabi ? if stdenv.hostPlatform.isFreeBSD then libcxxrt else null
+, libcxxrt, libunwind
+, enableShared ? !stdenv.hostPlatform.isStatic
+}:
+
+# external cxxabi is not supported on Darwin as the build will not link libcxx
+# properly and not re-export the cxxabi symbols into libcxx
+# https://github.com/NixOS/nixpkgs/issues/166205
+# https://github.com/NixOS/nixpkgs/issues/269548
+assert cxxabi == null || !stdenv.hostPlatform.isDarwin;
+let
+  basename = "libcxx";
+  cxxabiName = "lib${if cxxabi == null then "cxxabi" else cxxabi.libName}";
+  runtimes = [ "libcxx" ] ++ lib.optional (cxxabi == null) "libcxxabi";
+
+  # Note: useLLVM is likely false for Darwin but true under pkgsLLVM
+  useLLVM = stdenv.hostPlatform.useLLVM or false;
+
+  cxxabiCMakeFlags = [
+    "-DLIBCXXABI_USE_LLVM_UNWINDER=OFF"
+  ] ++ lib.optionals (useLLVM && !stdenv.hostPlatform.isWasm) [
+    "-DLIBCXXABI_ADDITIONAL_LIBRARIES=unwind"
+    "-DLIBCXXABI_USE_COMPILER_RT=ON"
+  ] ++ lib.optionals stdenv.hostPlatform.isWasm [
+    "-DLIBCXXABI_ENABLE_THREADS=OFF"
+    "-DLIBCXXABI_ENABLE_EXCEPTIONS=OFF"
+  ] ++ lib.optionals (!enableShared) [
+    "-DLIBCXXABI_ENABLE_SHARED=OFF"
+  ];
+
+  cxxCMakeFlags = [
+    "-DLIBCXX_CXX_ABI=${cxxabiName}"
+  ] ++ lib.optionals (cxxabi != null) [
+    "-DLIBCXX_CXX_ABI_INCLUDE_PATHS=${lib.getDev cxxabi}/include"
+  ] ++ lib.optionals (stdenv.hostPlatform.isMusl || stdenv.hostPlatform.isWasi) [
+    "-DLIBCXX_HAS_MUSL_LIBC=1"
+  ] ++ lib.optionals (lib.versionAtLeast version "18" && !useLLVM && stdenv.hostPlatform.libc == "glibc" && !stdenv.hostPlatform.isStatic) [
+    "-DLIBCXX_ADDITIONAL_LIBRARIES=gcc_s"
+  ] ++ lib.optionals useLLVM [
+    "-DLIBCXX_USE_COMPILER_RT=ON"
+    # There's precedent for this in llvm-project/libcxx/cmake/caches.
+    # In a monorepo build you might do the following in the libcxxabi build:
+    #   -DLLVM_ENABLE_PROJECTS=libcxxabi;libunwinder
+    #   -DLIBCXXABI_STATICALLY_LINK_UNWINDER_IN_STATIC_LIBRARY=On
+    # libcxx appears to require unwind and doesn't pull it in via other means.
+    "-DLIBCXX_ADDITIONAL_LIBRARIES=unwind"
+  ] ++ lib.optionals stdenv.hostPlatform.isWasm [
+    "-DLIBCXX_ENABLE_THREADS=OFF"
+    "-DLIBCXX_ENABLE_FILESYSTEM=OFF"
+    "-DLIBCXX_ENABLE_EXCEPTIONS=OFF"
+  ] ++ lib.optionals (!enableShared) [
+    "-DLIBCXX_ENABLE_SHARED=OFF"
+  ];
+
+  cmakeFlags = [
+    "-DLLVM_ENABLE_RUNTIMES=${lib.concatStringsSep ";" runtimes}"
+  ] ++ lib.optionals stdenv.hostPlatform.isWasm [
+    "-DCMAKE_C_COMPILER_WORKS=ON"
+    "-DCMAKE_CXX_COMPILER_WORKS=ON"
+    "-DUNIX=ON" # Required otherwise libc++ fails to detect the correct linker
+  ] ++ cxxCMakeFlags
+    ++ lib.optionals (cxxabi == null) cxxabiCMakeFlags;
+
+in
+
+stdenv.mkDerivation rec {
+  pname = basename;
+  inherit version cmakeFlags;
+
+  src = runCommand "${pname}-src-${version}" {} (''
+    mkdir -p "$out/llvm"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/libcxx "$out"
+    cp -r ${monorepoSrc}/llvm/cmake "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/utils "$out/llvm"
+    cp -r ${monorepoSrc}/third-party "$out"
+    cp -r ${monorepoSrc}/runtimes "$out"
+  '' + lib.optionalString (cxxabi == null) ''
+    cp -r ${monorepoSrc}/libcxxabi "$out"
+  '');
+
+  outputs = [ "out" "dev" ];
+
+  patches = lib.optionals (stdenv.isDarwin && lib.versionOlder stdenv.hostPlatform.darwinMinVersion "10.13") [
+    # https://github.com/llvm/llvm-project/issues/64226
+    ./0001-darwin-10.12-mbstate_t-fix.patch
+  ];
+
+  postPatch = ''
+    cd runtimes
+  '';
+
+  preConfigure = lib.optionalString stdenv.hostPlatform.isMusl ''
+    patchShebangs utils/cat_files.py
+  '';
+
+  nativeBuildInputs = [ cmake ninja python3 ]
+    ++ lib.optional stdenv.isDarwin fixDarwinDylibNames
+    ++ lib.optional (cxxabi != null) lndir;
+
+  buildInputs = [ cxxabi ]
+    ++ lib.optionals (useLLVM && !stdenv.hostPlatform.isWasm) [ libunwind ];
+
+  # libc++.so is a linker script which expands to multiple libraries,
+  # libc++.so.1 and libc++abi.so or the external cxxabi. ld-wrapper doesn't
+  # support linker scripts so the external cxxabi needs to be symlinked in
+  postInstall = lib.optionalString (cxxabi != null) ''
+    lndir ${lib.getDev cxxabi}/include ''${!outputDev}/include/c++/v1
+    lndir ${lib.getLib cxxabi}/lib ''${!outputLib}/lib
+  '';
+
+  passthru = {
+    isLLVM = true;
+  };
+
+  meta = llvm_meta // {
+    homepage = "https://libcxx.llvm.org/";
+    description = "C++ standard library";
+    longDescription = ''
+      libc++ is an implementation of the C++ standard library, targeting C++11,
+      C++14 and above.
+    '';
+    # "All of the code in libc++ is dual licensed under the MIT license and the
+    # UIUC License (a BSD-like license)":
+    license = with lib.licenses; [ mit ncsa ];
+  };
+}
--- a/pkgs/development/compilers/llvm/18/libunwind/default.nix
+++ b/pkgs/development/compilers/llvm/18/libunwind/default.nix
@ -0,0 +1,54 @@
+{ lib, stdenv, llvm_meta, version
+, monorepoSrc, runCommand
+, cmake
+, ninja
+, python3
+, enableShared ? !stdenv.hostPlatform.isStatic
+}:
+
+stdenv.mkDerivation rec {
+  pname = "libunwind";
+  inherit version;
+
+  # I am not so comfortable giving libc++ and friends the whole monorepo as
+  # requested, so I filter it to what is needed.
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+    mkdir -p "$out/libcxx"
+    cp -r ${monorepoSrc}/libcxx/cmake "$out/libcxx"
+    cp -r ${monorepoSrc}/libcxx/utils "$out/libcxx"
+    mkdir -p "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/cmake "$out/llvm"
+    cp -r ${monorepoSrc}/llvm/utils "$out/llvm"
+    cp -r ${monorepoSrc}/runtimes "$out"
+  '';
+
+  sourceRoot = "${src.name}/runtimes";
+
+  postInstall = lib.optionalString (enableShared && !stdenv.hostPlatform.isDarwin) ''
+    # libcxxabi wants to link to libunwind_shared.so (?).
+    ln -s $out/lib/libunwind.so $out/lib/libunwind_shared.so
+  '';
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [ cmake ninja python3 ];
+
+  cmakeFlags = [
+    "-DLLVM_ENABLE_RUNTIMES=libunwind"
+  ] ++ lib.optional (!enableShared) "-DLIBUNWIND_ENABLE_SHARED=OFF";
+
+  meta = llvm_meta // {
+    # Details: https://github.com/llvm/llvm-project/blob/main/libunwind/docs/index.rst
+    homepage = "https://clang.llvm.org/docs/Toolchain.html#unwind-library";
+    description = "LLVM's unwinder library";
+    longDescription = ''
+      The unwind library provides a family of _Unwind_* functions implementing
+      the language-neutral stack unwinding portion of the Itanium C++ ABI (Level
+      I). It is a dependency of the C++ ABI library, and sometimes is a
+      dependency of other runtimes.
+    '';
+  };
+}
--- a/pkgs/development/compilers/llvm/18/lld/default.nix
+++ b/pkgs/development/compilers/llvm/18/lld/default.nix
@ -0,0 +1,57 @@
+{ lib, stdenv, llvm_meta
+, buildLlvmTools
+, monorepoSrc, runCommand
+, cmake
+, ninja
+, libxml2
+, libllvm
+, version
+}:
+
+stdenv.mkDerivation rec {
+  pname = "lld";
+  inherit version;
+
+  # Blank llvm dir just so relative path works
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+    mkdir -p "$out/libunwind"
+    cp -r ${monorepoSrc}/libunwind/include "$out/libunwind"
+    mkdir -p "$out/llvm"
+  '';
+
+  sourceRoot = "${src.name}/${pname}";
+
+  nativeBuildInputs = [ cmake ninja ];
+  buildInputs = [ libllvm libxml2 ];
+
+  patches = [
+    ./gnu-install-dirs.patch
+  ];
+
+  cmakeFlags = [
+    "-DLLD_INSTALL_PACKAGE_DIR=${placeholder "dev"}/lib/cmake/lld"
+  ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+    "-DLLVM_TABLEGEN_EXE=${buildLlvmTools.llvm}/bin/llvm-tblgen"
+  ];
+
+  # Musl's default stack size is too small for lld to be able to link Firefox.
+  LDFLAGS = lib.optionalString stdenv.hostPlatform.isMusl "-Wl,-z,stack-size=2097152";
+
+  outputs = [ "out" "lib" "dev" ];
+
+  meta = llvm_meta // {
+    homepage = "https://lld.llvm.org/";
+    description = "The LLVM linker (unwrapped)";
+    longDescription = ''
+      LLD is a linker from the LLVM project that is a drop-in replacement for
+      system linkers and runs much faster than them. It also provides features
+      that are useful for toolchain developers.
+      The linker supports ELF (Unix), PE/COFF (Windows), Mach-O (macOS), and
+      WebAssembly in descending order of completeness. Internally, LLD consists
+      of several different linkers.
+    '';
+  };
+}
--- a/pkgs/development/compilers/llvm/18/lld/gnu-install-dirs.patch
+++ b/pkgs/development/compilers/llvm/18/lld/gnu-install-dirs.patch
@ -0,0 +1,15 @@
+diff --git a/cmake/modules/AddLLD.cmake b/cmake/modules/AddLLD.cmake
+index d3924f7243d4..42a7cd62281c 100644
+--- a/cmake/modules/AddLLD.cmake
+++ b/cmake/modules/AddLLD.cmake
+@@ -18,8 +18,8 @@ macro(add_lld_library name)
+     install(TARGETS ${name}
+       COMPONENT ${name}
+       ${export_to_lldtargets}
+-      LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+-      ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+      LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}"
+      ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}"
+       RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
+ 
+     if (${ARG_SHARED} AND NOT CMAKE_CONFIGURATION_TYPES)
--- a/pkgs/development/compilers/llvm/18/lldb/cpu_subtype_arm64e_replacement.patch
+++ b/pkgs/development/compilers/llvm/18/lldb/cpu_subtype_arm64e_replacement.patch
@ -0,0 +1,12 @@
+diff --git a/source/Host/macosx/objcxx/HostInfoMacOSX.mm b/source/Host/macosx/objcxx/HostInfoMacOSX.mm
+--- a/source/Host/macosx/objcxx/HostInfoMacOSX.mm
+++ b/source/Host/macosx/objcxx/HostInfoMacOSX.mm
+@@ -233,7 +233,7 @@ void HostInfoMacOSX::ComputeHostArchitectureSupport(ArchSpec &arch_32,
+     len = sizeof(is_64_bit_capable);
+     ::sysctlbyname("hw.cpu64bit_capable", &is_64_bit_capable, &len, NULL, 0);
+ 
+-    if (cputype == CPU_TYPE_ARM64 && cpusubtype == CPU_SUBTYPE_ARM64E) {
+    if (cputype == CPU_TYPE_ARM64 && cpusubtype == ((cpu_subtype_t) 2)) { // CPU_SUBTYPE_ARM64E is not available in the macOS 10.12 headers
+       // The arm64e architecture is a preview. Pretend the host architecture
+       // is arm64.
+       cpusubtype = CPU_SUBTYPE_ARM64_ALL;
--- a/pkgs/development/compilers/llvm/18/lldb/procfs.patch
+++ b/pkgs/development/compilers/llvm/18/lldb/procfs.patch
@ -0,0 +1,46 @@
+--- a/source/Plugins/Process/Linux/Procfs.h
+++ b/source/Plugins/Process/Linux/Procfs.h
+@@ -10,6 +10,13 @@
+ // sys/procfs.h on Android/Linux for all supported architectures.
+ 
+ #include <sys/ptrace.h>
+#include <asm/ptrace.h>
+
+// on i686 preprocessor symbols with these register names are defined as
+// numeric constants; these symbols clash with identifier names used in
+// `llvm/Support/VirtualFileSystem.h` and `llvm/ADT/SmallVector.h`
+#undef FS
+#undef CS
+ 
+ #include "lldb/lldb-types.h"
+ 
+@@ -17,23 +24,13 @@
+ 
+ #include <vector>
+ 
+-#ifdef __ANDROID__
+-#if defined(__arm64__) || defined(__aarch64__)
+-typedef unsigned long elf_greg_t;
+-typedef elf_greg_t
+-    elf_gregset_t[(sizeof(struct user_pt_regs) / sizeof(elf_greg_t))];
+-typedef struct user_fpsimd_state elf_fpregset_t;
+-#ifndef NT_FPREGSET
+-#define NT_FPREGSET NT_PRFPREG
+-#endif // NT_FPREGSET
+-#elif defined(__mips__)
+-#ifndef NT_FPREGSET
+-#define NT_FPREGSET NT_PRFPREG
+-#endif // NT_FPREGSET
+-#endif
+-#else // __ANDROID__
+#if !defined(__GLIBC__) && defined(__powerpc__)
+#define pt_regs musl_pt_regs
+#include <sys/procfs.h>
+#undef pt_regs
+#else
+ #include <sys/procfs.h>
+-#endif // __ANDROID__
+#endif
+ 
+ namespace lldb_private {
+ namespace process_linux {
--- a/pkgs/development/compilers/llvm/18/llvm/default.nix
+++ b/pkgs/development/compilers/llvm/18/llvm/default.nix
@ -0,0 +1,439 @@
+{ lib, stdenv, llvm_meta
+, pkgsBuildBuild
+, monorepoSrc
+, runCommand
+, cmake
+, darwin
+, ninja
+, python3
+, python3Packages
+, libffi
+, enableGoldPlugin ? true
+, libbfd
+, libpfm
+, libxml2
+, ncurses
+, version
+, release_version
+, zlib
+, which
+, sysctl
+, buildLlvmTools
+, debugVersion ? false
+, doCheck ? (!stdenv.isx86_32 /* TODO: why */) && (!stdenv.hostPlatform.isMusl)
+  && (stdenv.hostPlatform == stdenv.buildPlatform)
+, enableManpages ? false
+, enableSharedLibraries ? !stdenv.hostPlatform.isStatic
+, enablePFM ? stdenv.isLinux /* PFM only supports Linux */
+  # broken for Ampere eMAG 8180 (c2.large.arm on Packet) #56245
+  # broken for the armv7l builder
+  && !stdenv.hostPlatform.isAarch
+, enablePolly ? true
+}:
+
+let
+  inherit (lib) optional optionals optionalString;
+
+  # Used when creating a version-suffixed symlink of libLLVM.dylib
+  shortVersion = with lib;
+    concatStringsSep "." (take 1 (splitString "." release_version));
+
+  # Ordinarily we would just the `doCheck` and `checkDeps` functionality
+  # `mkDerivation` gives us to manage our test dependencies (instead of breaking
+  # out `doCheck` as a package level attribute).
+  #
+  # Unfortunately `lit` does not forward `$PYTHONPATH` to children processes, in
+  # particular the children it uses to do feature detection.
+  #
+  # This means that python deps we add to `checkDeps` (which the python
+  # interpreter is made aware of via `$PYTHONPATH` – populated by the python
+  # setup hook) are not picked up by `lit` which causes it to skip tests.
+  #
+  # Adding `python3.withPackages (ps: [ ... ])` to `checkDeps` also doesn't work
+  # because this package is shadowed in `$PATH` by the regular `python3`
+  # package.
+  #
+  # So, we "manually" assemble one python derivation for the package to depend
+  # on, taking into account whether checks are enabled or not:
+  python = if doCheck then
+    # Note that we _explicitly_ ask for a python interpreter for our host
+    # platform here; the splicing that would ordinarily take care of this for
+    # us does not seem to work once we use `withPackages`.
+    let
+      checkDeps = ps: with ps; [ psutil ];
+    in pkgsBuildBuild.targetPackages.python3.withPackages checkDeps
+  else python3;
+
+in
+
+stdenv.mkDerivation (rec {
+  pname = "llvm";
+  inherit version;
+
+  src = runCommand "${pname}-src-${version}" {} (''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+    cp -r ${monorepoSrc}/third-party "$out"
+  '' + lib.optionalString enablePolly ''
+    chmod u+w "$out/${pname}/tools"
+    cp -r ${monorepoSrc}/polly "$out/${pname}/tools"
+  '');
+
+  sourceRoot = "${src.name}/${pname}";
+
+  outputs = [ "out" "lib" "dev" "python" ];
+
+  nativeBuildInputs = [ cmake ninja python ]
+    ++ optionals enableManpages [
+    # Note: we intentionally use `python3Packages` instead of `python3.pkgs`;
+    # splicing does *not* work with the latter. (TODO: fix)
+    python3Packages.sphinx
+  ] ++ optionals (lib.versionOlder version "18" && enableManpages) [
+    python3Packages.recommonmark
+  ] ++ optionals (lib.versionAtLeast version "18" && enableManpages) [
+    python3Packages.myst-parser
+  ];
+
+  buildInputs = [ libxml2 libffi ]
+    ++ optional enablePFM libpfm; # exegesis
+
+  propagatedBuildInputs = [ ncurses zlib ];
+
+  nativeCheckInputs = [
+    which
+  ] ++ lib.optional stdenv.isDarwin sysctl;
+
+  patches = [
+    ./gnu-install-dirs.patch
+
+    # Running the tests involves invoking binaries (like `opt`) that depend on
+    # the LLVM dylibs and reference them by absolute install path (i.e. their
+    # nix store path).
+    #
+    # Because we have not yet run the install phase (we're running these tests
+    # as part of `checkPhase` instead of `installCheckPhase`) these absolute
+    # paths do not exist yet; to work around this we point the loader (`ld` on
+    # unix, `dyld` on macOS) at the `lib` directory which will later become this
+    # package's `lib` output.
+    #
+    # Previously we would just set `LD_LIBRARY_PATH` to include the build `lib`
+    # dir but:
+    #   - this doesn't generalize well to other platforms; `lit` doesn't forward
+    #     `DYLD_LIBRARY_PATH` (macOS):
+    #     + https://github.com/llvm/llvm-project/blob/0d89963df354ee309c15f67dc47c8ab3cb5d0fb2/llvm/utils/lit/lit/TestingConfig.py#L26
+    #   - even if `lit` forwarded this env var, we actually cannot set
+    #     `DYLD_LIBRARY_PATH` in the child processes `lit` launches because
+    #     `DYLD_LIBRARY_PATH` (and `DYLD_FALLBACK_LIBRARY_PATH`) is cleared for
+    #     "protected processes" (i.e. the python interpreter that runs `lit`):
+    #     https://stackoverflow.com/a/35570229
+    #   - other LLVM subprojects deal with this issue by having their `lit`
+    #     configuration set these env vars for us; it makes sense to do the same
+    #     for LLVM:
+    #     + https://github.com/llvm/llvm-project/blob/4c106cfdf7cf7eec861ad3983a3dd9a9e8f3a8ae/clang-tools-extra/test/Unit/lit.cfg.py#L22-L31
+    #
+    # !!! TODO: look into upstreaming this patch
+    ./llvm-lit-cfg-add-libs-to-dylib-path.patch
+
+    # `lit` has a mode where it executes run lines as a shell script which is
+    # constructs; this is problematic for macOS because it means that there's
+    # another process in between `lit` and the binaries being tested. As noted
+    # above, this means that `DYLD_LIBRARY_PATH` is cleared which means that our
+    # tests fail with dyld errors.
+    #
+    # To get around this we patch `lit` to reintroduce `DYLD_LIBRARY_PATH`, when
+    # present in the test configuration.
+    #
+    # It's not clear to me why this isn't an issue for LLVM developers running
+    # on macOS (nothing about this _seems_ nix specific)..
+    ./lit-shell-script-runner-set-dyld-library-path.patch
+  ] ++ lib.optionals enablePolly [
+    ./gnu-install-dirs-polly.patch
+
+    # Just like the `llvm-lit-cfg` patch, but for `polly`.
+    ./polly-lit-cfg-add-libs-to-dylib-path.patch
+  ];
+
+  postPatch = optionalString stdenv.isDarwin ''
+    substituteInPlace cmake/modules/AddLLVM.cmake \
+      --replace 'set(_install_name_dir INSTALL_NAME_DIR "@rpath")' "set(_install_name_dir)" \
+      --replace 'set(_install_rpath "@loader_path/../''${CMAKE_INSTALL_LIBDIR}''${LLVM_LIBDIR_SUFFIX}" ''${extra_libdir})' ""
+
+    # As of LLVM 15, marked as XFAIL on arm64 macOS but lit doesn't seem to pick
+    # this up: https://github.com/llvm/llvm-project/blob/c344d97a125b18f8fed0a64aace73c49a870e079/llvm/test/MC/ELF/cfi-version.ll#L7
+    rm test/MC/ELF/cfi-version.ll
+
+    # This test tries to call `sw_vers` by absolute path (`/usr/bin/sw_vers`)
+    # and thus fails under the sandbox:
+    substituteInPlace unittests/TargetParser/Host.cpp \
+      --replace '/usr/bin/sw_vers' "${(builtins.toString darwin.DarwinTools) + "/bin/sw_vers" }"
+
+    # This test tries to call the intrinsics `@llvm.roundeven.f32` and
+    # `@llvm.roundeven.f64` which seem to (incorrectly?) lower to `roundevenf`
+    # and `roundeven` on macOS.
+    #
+    # However these functions are glibc specific so the test fails:
+    #   - https://www.gnu.org/software/gnulib/manual/html_node/roundevenf.html
+    #   - https://www.gnu.org/software/gnulib/manual/html_node/roundeven.html
+    #
+    substituteInPlace test/ExecutionEngine/Interpreter/intrinsics.ll \
+      --replace "%roundeven32 = call float @llvm.roundeven.f32(float 0.000000e+00)" "" \
+      --replace "%roundeven64 = call double @llvm.roundeven.f64(double 0.000000e+00)" ""
+
+    # fails when run in sandbox
+    substituteInPlace unittests/Support/VirtualFileSystemTest.cpp \
+      --replace "PhysicalFileSystemWorkingDirFailure" "DISABLED_PhysicalFileSystemWorkingDirFailure"
+  '' + optionalString (stdenv.isDarwin && stdenv.hostPlatform.isx86) ''
+    # This test fails on darwin x86_64 because `sw_vers` reports a different
+    # macOS version than what LLVM finds by reading
+    # `/System/Library/CoreServices/SystemVersion.plist` (which is passed into
+    # the sandbox on macOS).
+    #
+    # The `sw_vers` provided by nixpkgs reports the macOS version associated
+    # with the `CoreFoundation` framework with which it was built. Because
+    # nixpkgs pins the SDK for `aarch64-darwin` and `x86_64-darwin` what
+    # `sw_vers` reports is not guaranteed to match the macOS version of the host
+    # that's building this derivation.
+    #
+    # Astute readers will note that we only _patch_ this test on aarch64-darwin
+    # (to use the nixpkgs provided `sw_vers`) instead of disabling it outright.
+    # So why does this test pass on aarch64?
+    #
+    # Well, it seems that `sw_vers` on aarch64 actually links against the _host_
+    # CoreFoundation framework instead of the nixpkgs provided one.
+    #
+    # Not entirely sure what the right fix is here. I'm assuming aarch64
+    # `sw_vers` doesn't intentionally link against the host `CoreFoundation`
+    # (still digging into how this ends up happening, will follow up) but that
+    # aside I think the more pertinent question is: should we be patching LLVM's
+    # macOS version detection logic to use `sw_vers` instead of reading host
+    # paths? This *is* a way in which details about builder machines can creep
+    # into the artifacts that are produced, affecting reproducibility, but it's
+    # not clear to me when/where/for what this even gets used in LLVM.
+    #
+    # TODO(@rrbutani): fix/follow-up
+    substituteInPlace unittests/TargetParser/Host.cpp \
+      --replace "getMacOSHostVersion" "DISABLED_getMacOSHostVersion"
+
+    # This test fails with a `dysmutil` crash; have not yet dug into what's
+    # going on here (TODO(@rrbutani)).
+    rm test/tools/dsymutil/ARM/obfuscated.test
+  '' + ''
+    # FileSystem permissions tests fail with various special bits
+    substituteInPlace unittests/Support/CMakeLists.txt \
+      --replace "Path.cpp" ""
+    rm unittests/Support/Path.cpp
+    substituteInPlace unittests/IR/CMakeLists.txt \
+      --replace "PassBuilderCallbacksTest.cpp" ""
+    rm unittests/IR/PassBuilderCallbacksTest.cpp
+    rm test/tools/llvm-objcopy/ELF/mirror-permissions-unix.test
+
+    # Fails in the presence of anti-virus software or other intrusion-detection software that
+    # modifies the atime when run. See #284056.
+    rm test/tools/llvm-objcopy/ELF/strip-preserve-atime.test
+  '' + optionalString stdenv.hostPlatform.isMusl ''
+    patch -p1 -i ${../../common/llvm/TLI-musl.patch}
+    substituteInPlace unittests/Support/CMakeLists.txt \
+      --replace "add_subdirectory(DynamicLibrary)" ""
+    rm unittests/Support/DynamicLibrary/DynamicLibraryTest.cpp
+    # valgrind unhappy with musl or glibc, but fails w/musl only
+    rm test/CodeGen/AArch64/wineh4.mir
+  '' + optionalString stdenv.hostPlatform.isAarch32 ''
+    # skip failing X86 test cases on 32-bit ARM
+    rm test/DebugInfo/X86/convert-debugloc.ll
+    rm test/DebugInfo/X86/convert-inlined.ll
+    rm test/DebugInfo/X86/convert-linked.ll
+    rm test/tools/dsymutil/X86/op-convert.test
+    rm test/tools/gold/X86/split-dwarf.ll
+    rm test/tools/llvm-dwarfdump/X86/prettyprint_types.s
+    rm test/tools/llvm-dwarfdump/X86/simplified-template-names.s
+    rm test/CodeGen/RISCV/attributes.ll
+    rm test/CodeGen/RISCV/xtheadmempair.ll
+  '' + optionalString (stdenv.hostPlatform.system == "armv6l-linux") ''
+    # Seems to require certain floating point hardware (NEON?)
+    rm test/ExecutionEngine/frem.ll
+  '' + ''
+    patchShebangs test/BugPoint/compile-custom.ll.py
+  '';
+
+  preConfigure = ''
+    # Workaround for configure flags that need to have spaces
+    cmakeFlagsArray+=(
+      -DLLVM_LIT_ARGS="-svj''${NIX_BUILD_CORES} --no-progress-bar"
+    )
+  '';
+
+  # Defensive check: some paths (that we make symlinks to) depend on the release
+  # version, for example:
+  #  - https://github.com/llvm/llvm-project/blob/406bde9a15136254f2b10d9ef3a42033b3cb1b16/clang/lib/Headers/CMakeLists.txt#L185
+  #
+  # So we want to sure that the version in the source matches the release
+  # version we were given.
+  #
+  # We do this check here, in the LLVM build, because it happens early.
+  postConfigure = let
+    v = lib.versions;
+    major = v.major release_version;
+    minor = v.minor release_version;
+    patch = v.patch release_version;
+  in ''
+    # $1: part, $2: expected
+    check_version() {
+      part="''${1^^}"
+      part="$(cat include/llvm/Config/llvm-config.h  | grep "#define LLVM_VERSION_''${part} " | cut -d' ' -f3)"
+
+      if [[ "$part" != "$2" ]]; then
+        echo >&2 \
+          "mismatch in the $1 version! we have version ${release_version}" \
+          "and expected the $1 version to be '$2'; the source has '$part' instead"
+        exit 3
+      fi
+    }
+
+    check_version major ${major}
+    check_version minor ${minor}
+    check_version patch ${patch}
+  '';
+
+  # E.g. mesa.drivers use the build-id as a cache key (see #93946):
+  LDFLAGS = optionalString (enableSharedLibraries && !stdenv.isDarwin) "-Wl,--build-id=sha1";
+
+  hardeningDisable = [ "trivialautovarinit" ];
+
+  cmakeBuildType = if debugVersion then "Debug" else "Release";
+
+  cmakeFlags = with stdenv; let
+    # These flags influence llvm-config's BuildVariables.inc in addition to the
+    # general build. We need to make sure these are also passed via
+    # CROSS_TOOLCHAIN_FLAGS_NATIVE when cross-compiling or llvm-config-native
+    # will return different results from the cross llvm-config.
+    #
+    # Some flags don't need to be repassed because LLVM already does so (like
+    # CMAKE_BUILD_TYPE), others are irrelevant to the result.
+    flagsForLlvmConfig = [
+      "-DLLVM_INSTALL_PACKAGE_DIR=${placeholder "dev"}/lib/cmake/llvm"
+      "-DLLVM_ENABLE_RTTI=ON"
+    ] ++ optionals enableSharedLibraries [
+      "-DLLVM_LINK_LLVM_DYLIB=ON"
+    ];
+  in flagsForLlvmConfig ++ [
+    "-DLLVM_INSTALL_UTILS=ON"  # Needed by rustc
+    "-DLLVM_BUILD_TESTS=${if doCheck then "ON" else "OFF"}"
+    "-DLLVM_ENABLE_FFI=ON"
+    "-DLLVM_HOST_TRIPLE=${stdenv.hostPlatform.config}"
+    "-DLLVM_DEFAULT_TARGET_TRIPLE=${stdenv.hostPlatform.config}"
+    "-DLLVM_ENABLE_DUMP=ON"
+  ] ++ optionals stdenv.hostPlatform.isStatic [
+    # Disables building of shared libs, -fPIC is still injected by cc-wrapper
+    "-DLLVM_ENABLE_PIC=OFF"
+    "-DLLVM_BUILD_STATIC=ON"
+    "-DLLVM_LINK_LLVM_DYLIB=off"
+    # libxml2 needs to be disabled because the LLVM build system ignores its .la
+    # file and doesn't link zlib as well.
+    # https://github.com/ClangBuiltLinux/tc-build/issues/150#issuecomment-845418812
+    "-DLLVM_ENABLE_LIBXML2=OFF"
+  ] ++ optionals enableManpages [
+    "-DLLVM_BUILD_DOCS=ON"
+    "-DLLVM_ENABLE_SPHINX=ON"
+    "-DSPHINX_OUTPUT_MAN=ON"
+    "-DSPHINX_OUTPUT_HTML=OFF"
+    "-DSPHINX_WARNINGS_AS_ERRORS=OFF"
+  ] ++ optionals enableGoldPlugin [
+    "-DLLVM_BINUTILS_INCDIR=${libbfd.dev}/include"
+  ] ++ optionals isDarwin [
+    "-DLLVM_ENABLE_LIBCXX=ON"
+    "-DCAN_TARGET_i386=false"
+  ] ++ optionals ((stdenv.hostPlatform != stdenv.buildPlatform) && !(stdenv.buildPlatform.canExecute stdenv.hostPlatform)) [
+    "-DCMAKE_CROSSCOMPILING=True"
+    "-DLLVM_TABLEGEN=${buildLlvmTools.llvm}/bin/llvm-tblgen"
+    (
+      let
+        nativeCC = pkgsBuildBuild.targetPackages.stdenv.cc;
+        nativeBintools = nativeCC.bintools.bintools;
+        nativeToolchainFlags = [
+          "-DCMAKE_C_COMPILER=${nativeCC}/bin/${nativeCC.targetPrefix}cc"
+          "-DCMAKE_CXX_COMPILER=${nativeCC}/bin/${nativeCC.targetPrefix}c++"
+          "-DCMAKE_AR=${nativeBintools}/bin/${nativeBintools.targetPrefix}ar"
+          "-DCMAKE_STRIP=${nativeBintools}/bin/${nativeBintools.targetPrefix}strip"
+          "-DCMAKE_RANLIB=${nativeBintools}/bin/${nativeBintools.targetPrefix}ranlib"
+        ];
+        # We need to repass the custom GNUInstallDirs values, otherwise CMake
+        # will choose them for us, leading to wrong results in llvm-config-native
+        nativeInstallFlags = [
+          "-DCMAKE_INSTALL_PREFIX=${placeholder "out"}"
+          "-DCMAKE_INSTALL_BINDIR=${placeholder "out"}/bin"
+          "-DCMAKE_INSTALL_INCLUDEDIR=${placeholder "dev"}/include"
+          "-DCMAKE_INSTALL_LIBDIR=${placeholder "lib"}/lib"
+          "-DCMAKE_INSTALL_LIBEXECDIR=${placeholder "lib"}/libexec"
+        ];
+      in "-DCROSS_TOOLCHAIN_FLAGS_NATIVE:list="
+      + lib.concatStringsSep ";" (lib.concatLists [
+        flagsForLlvmConfig
+        nativeToolchainFlags
+        nativeInstallFlags
+      ])
+    )
+  ];
+
+  postInstall = ''
+    mkdir -p $python/share
+    mv $out/share/opt-viewer $python/share/opt-viewer
+    moveToOutput "bin/llvm-config*" "$dev"
+    substituteInPlace "$dev/lib/cmake/llvm/LLVMExports-${if debugVersion then "debug" else "release"}.cmake" \
+      --replace "\''${_IMPORT_PREFIX}/lib/lib" "$lib/lib/lib" \
+      --replace "$out/bin/llvm-config" "$dev/bin/llvm-config"
+    substituteInPlace "$dev/lib/cmake/llvm/LLVMConfig.cmake" \
+      --replace 'set(LLVM_BINARY_DIR "''${LLVM_INSTALL_PREFIX}")' 'set(LLVM_BINARY_DIR "'"$lib"'")'
+  ''
+  + optionalString (stdenv.isDarwin && enableSharedLibraries) ''
+    ln -s $lib/lib/libLLVM.dylib $lib/lib/libLLVM-${release_version}.dylib
+  ''
+  + optionalString (stdenv.buildPlatform != stdenv.hostPlatform) ''
+    cp NATIVE/bin/llvm-config $dev/bin/llvm-config-native
+  '';
+
+  inherit doCheck;
+
+  checkTarget = "check-all";
+
+  # For the update script:
+  passthru.monorepoSrc = monorepoSrc;
+
+  requiredSystemFeatures = [ "big-parallel" ];
+  meta = llvm_meta // {
+    homepage = "https://llvm.org/";
+    description = "A collection of modular and reusable compiler and toolchain technologies";
+    longDescription = ''
+      The LLVM Project is a collection of modular and reusable compiler and
+      toolchain technologies. Despite its name, LLVM has little to do with
+      traditional virtual machines. The name "LLVM" itself is not an acronym; it
+      is the full name of the project.
+      LLVM began as a research project at the University of Illinois, with the
+      goal of providing a modern, SSA-based compilation strategy capable of
+      supporting both static and dynamic compilation of arbitrary programming
+      languages. Since then, LLVM has grown to be an umbrella project consisting
+      of a number of subprojects, many of which are being used in production by
+      a wide variety of commercial and open source projects as well as being
+      widely used in academic research. Code in the LLVM project is licensed
+      under the "Apache 2.0 License with LLVM exceptions".
+    '';
+  };
+} // lib.optionalAttrs enableManpages {
+  pname = "llvm-manpages";
+
+  propagatedBuildInputs = [];
+
+  ninjaFlags = [ "docs-llvm-man" ];
+  installTargets = [ "install-docs-llvm-man" ];
+
+  postPatch = null;
+  postInstall = null;
+
+  outputs = [ "out" ];
+
+  doCheck = false;
+
+  meta = llvm_meta // {
+    description = "man pages for LLVM ${version}";
+  };
+})
--- a/pkgs/development/compilers/llvm/18/llvm/gnu-install-dirs-polly.patch
+++ b/pkgs/development/compilers/llvm/18/llvm/gnu-install-dirs-polly.patch
@ -0,0 +1,13 @@
+--- a/tools/polly/cmake/polly_macros.cmake	2024-03-15 17:36:20.550893344 -0700
+++ b/tools/polly/cmake/polly_macros.cmake	2024-03-15 17:37:06.277332960 -0700
+@@ -45,8 +45,8 @@
+     install(TARGETS ${name}
+       COMPONENT ${name}
+       EXPORT LLVMExports
+-      LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX}
+-      ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX})
+      LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}
+      ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX})
+     add_llvm_install_targets(install-${name}
+       COMPONENT ${name})
+   endif()
--- a/pkgs/development/compilers/llvm/18/llvm/gnu-install-dirs.patch
+++ b/pkgs/development/compilers/llvm/18/llvm/gnu-install-dirs.patch
@ -0,0 +1,137 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 471817d68286..c51463304159 100644
+--- a/CMakeLists.txt
+++ b/CMakeLists.txt
+@@ -1010,7 +1010,7 @@ if (NOT TENSORFLOW_AOT_PATH STREQUAL "")
+   add_subdirectory(${TENSORFLOW_AOT_PATH}/xla_aot_runtime_src
+     ${CMAKE_ARCHIVE_OUTPUT_DIRECTORY}/tf_runtime)
+   install(TARGETS tf_xla_runtime EXPORT LLVMExports
+-    ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT tf_xla_runtime)
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX} COMPONENT tf_xla_runtime)
+   set_property(GLOBAL APPEND PROPERTY LLVM_EXPORTS tf_xla_runtime)
+   # Once we add more modules, we should handle this more automatically.
+   if (DEFINED LLVM_OVERRIDE_MODEL_HEADER_INLINERSIZEMODEL)
+diff --git a/cmake/modules/AddLLVM.cmake b/cmake/modules/AddLLVM.cmake
+index 230620c37027..dd16cab1835e 100644
+--- a/cmake/modules/AddLLVM.cmake
+++ b/cmake/modules/AddLLVM.cmake
+@@ -876,8 +876,8 @@ macro(add_llvm_library name)
+       get_target_export_arg(${name} LLVM export_to_llvmexports ${umbrella})
+       install(TARGETS ${name}
+               ${export_to_llvmexports}
+-              LIBRARY DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT ${name}
+-              ARCHIVE DESTINATION lib${LLVM_LIBDIR_SUFFIX} COMPONENT ${name}
+              LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" COMPONENT ${name}
+              ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" COMPONENT ${name}
+               RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}" COMPONENT ${name})
+ 
+       if (NOT LLVM_ENABLE_IDE)
+@@ -2069,7 +2069,7 @@ function(llvm_install_library_symlink name dest type)
+     set(LLVM_LINK_OR_COPY copy)
+   endif()
+ 
+-  set(output_dir lib${LLVM_LIBDIR_SUFFIX})
+  set(output_dir ${CMAKE_INSTALL_FULL_LIBDIR}${LLVM_LIBDIR_SUFFIX})
+   if(WIN32 AND "${type}" STREQUAL "SHARED")
+     set(output_dir "${CMAKE_INSTALL_BINDIR}")
+   endif()
+@@ -2344,16 +2344,37 @@ function(llvm_setup_rpath name)
+ 
+   if (APPLE)
+     set(_install_name_dir INSTALL_NAME_DIR "@rpath")
+-    set(_install_rpath "@loader_path/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+    set(_install_rpath ${extra_libdir})
+   elseif(${CMAKE_SYSTEM_NAME} MATCHES "AIX" AND BUILD_SHARED_LIBS)
+     # $ORIGIN is not interpreted at link time by aix ld.
+     # Since BUILD_SHARED_LIBS is only recommended for use by developers,
+     # hardcode the rpath to build/install lib dir first in this mode.
+     # FIXME: update this when there is better solution.
+-    set(_install_rpath "${LLVM_LIBRARY_OUTPUT_INTDIR}" "${CMAKE_INSTALL_PREFIX}/lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+    set(_install_rpath "${LLVM_LIBRARY_OUTPUT_INTDIR}" "${CMAKE_INSTALL_FULL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+   elseif(UNIX)
+-    set(_build_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+-    set(_install_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}")
+    # Note that we add `extra_libdir` (aka `LLVM_LIBRARY_DIR` in our case) back
+    # to `_install_rpath` here.
+    #
+    # In nixpkgs we do not build and install LLVM alongside rdeps of LLVM (i.e.
+    # clang); instead LLVM is its own package and thus lands at its own nix
+    # store path. This makes it so that the default relative rpath (`../lib/`)
+    # does not point at the LLVM shared objects.
+    #
+    # More discussion here:
+    #   - https://github.com/NixOS/nixpkgs/pull/235624#discussion_r1220150329
+    #   - https://reviews.llvm.org/D146918 (16.0.5+)
+    #
+    # Note that we leave `extra_libdir` in `_build_rpath`: without FHS there is
+    # no potential that this will result in us pulling in the "wrong" LLVM.
+    # Adding this to the build rpath means we aren't forced to use
+    # `installCheckPhase` instead of `checkPhase` (i.e. binaries in the build
+    # dir, pre-install, will have the right rpath for LLVM).
+    #
+    # As noted in the differential above, an alternative solution is to have
+    # all rdeps of nixpkgs' LLVM (that use the AddLLVM.cmake machinery) set
+    # `CMAKE_INSTALL_RPATH`.
+    set(_build_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+    set(_install_rpath ${extra_libdir})
+     if(${CMAKE_SYSTEM_NAME} MATCHES "(FreeBSD|DragonFly)")
+       set_property(TARGET ${name} APPEND_STRING PROPERTY
+                    LINK_FLAGS " -Wl,-z,origin ")
+diff --git a/cmake/modules/AddOCaml.cmake b/cmake/modules/AddOCaml.cmake
+index 891c9e6d618c..8d963f3b0069 100644
+--- a/cmake/modules/AddOCaml.cmake
+++ b/cmake/modules/AddOCaml.cmake
+@@ -147,9 +147,9 @@ function(add_ocaml_library name)
+   endforeach()
+ 
+   if( APPLE )
+-    set(ocaml_rpath "@executable_path/../../../lib${LLVM_LIBDIR_SUFFIX}")
+    set(ocaml_rpath ${LLVM_LIBRARY_DIR})
+   elseif( UNIX )
+-    set(ocaml_rpath "\\$ORIGIN/../../../lib${LLVM_LIBDIR_SUFFIX}")
+    set(ocaml_rpath ${LLVM_LIBRARY_DIR})
+   endif()
+   list(APPEND ocaml_flags "-ldopt" "-Wl,-rpath,${ocaml_rpath}")
+ 
+diff --git a/cmake/modules/CMakeLists.txt b/cmake/modules/CMakeLists.txt
+index d99af79aa38e..21e794224b99 100644
+--- a/cmake/modules/CMakeLists.txt
+++ b/cmake/modules/CMakeLists.txt
+@@ -127,7 +127,7 @@ set(LLVM_CONFIG_INCLUDE_DIRS
+   )
+ list(REMOVE_DUPLICATES LLVM_CONFIG_INCLUDE_DIRS)
+ 
+-extend_path(LLVM_CONFIG_LIBRARY_DIR "\${LLVM_INSTALL_PREFIX}" "lib\${LLVM_LIBDIR_SUFFIX}")
+extend_path(LLVM_CONFIG_LIBRARY_DIR "\${LLVM_INSTALL_PREFIX}" "${CMAKE_INSTALL_LIBDIR}\${LLVM_LIBDIR_SUFFIX}")
+ set(LLVM_CONFIG_LIBRARY_DIRS
+   "${LLVM_CONFIG_LIBRARY_DIR}"
+   # FIXME: Should there be other entries here?
+diff --git a/tools/llvm-config/BuildVariables.inc.in b/tools/llvm-config/BuildVariables.inc.in
+index 370005cd8d7d..7e790bc52111 100644
+--- a/tools/llvm-config/BuildVariables.inc.in
+++ b/tools/llvm-config/BuildVariables.inc.in
+@@ -23,6 +23,7 @@
+ #define LLVM_CXXFLAGS "@LLVM_CXXFLAGS@"
+ #define LLVM_BUILDMODE "@LLVM_BUILDMODE@"
+ #define LLVM_LIBDIR_SUFFIX "@LLVM_LIBDIR_SUFFIX@"
+#define LLVM_INSTALL_LIBDIR "@CMAKE_INSTALL_LIBDIR@"
+ #define LLVM_INSTALL_INCLUDEDIR "@CMAKE_INSTALL_INCLUDEDIR@"
+ #define LLVM_INSTALL_PACKAGE_DIR "@LLVM_INSTALL_PACKAGE_DIR@"
+ #define LLVM_TARGETS_BUILT "@LLVM_TARGETS_BUILT@"
+diff --git a/tools/llvm-config/llvm-config.cpp b/tools/llvm-config/llvm-config.cpp
+index e86eb2b44b10..f63e207e792e 100644
+--- a/tools/llvm-config/llvm-config.cpp
+++ b/tools/llvm-config/llvm-config.cpp
+@@ -366,7 +366,11 @@ int main(int argc, char **argv) {
+       sys::fs::make_absolute(ActivePrefix, Path);
+       ActiveBinDir = std::string(Path.str());
+     }
+-    ActiveLibDir = ActivePrefix + "/lib" + LLVM_LIBDIR_SUFFIX;
+    {
+      SmallString<256> Path(LLVM_INSTALL_LIBDIR LLVM_LIBDIR_SUFFIX);
+      sys::fs::make_absolute(ActivePrefix, Path);
+      ActiveLibDir = std::string(Path.str());
+    }
+     {
+       SmallString<256> Path(LLVM_INSTALL_PACKAGE_DIR);
+       sys::fs::make_absolute(ActivePrefix, Path);
--- a/pkgs/development/compilers/llvm/18/llvm/lit-shell-script-runner-set-dyld-library-path.patch
+++ b/pkgs/development/compilers/llvm/18/llvm/lit-shell-script-runner-set-dyld-library-path.patch
@ -0,0 +1,12 @@
+--- a/utils/lit/lit/TestRunner.py	2024-03-15 17:27:53.170780798 -0700
+++ b/utils/lit/lit/TestRunner.py	2024-03-15 17:28:43.277447791 -0700
+@@ -1183,6 +1183,9 @@
+         f.write("@echo on\n")
+         f.write("\n@if %ERRORLEVEL% NEQ 0 EXIT\n".join(commands))
+     else:
+        if "DYLD_LIBRARY_PATH" in test.config.environment:
+            f.write(f'export DYLD_LIBRARY_PATH="{test.config.environment["DYLD_LIBRARY_PATH"]}"\n')
+
+         for i, ln in enumerate(commands):
+             match = re.fullmatch(kPdbgRegex, ln)
+             if match:
--- a/pkgs/development/compilers/llvm/18/llvm/llvm-lit-cfg-add-libs-to-dylib-path.patch
+++ b/pkgs/development/compilers/llvm/18/llvm/llvm-lit-cfg-add-libs-to-dylib-path.patch
@ -0,0 +1,80 @@
+diff --git a/test/Unit/lit.cfg.py b/test/Unit/lit.cfg.py
+index 81e8dc04acea..479ff95681e2 100644
+--- a/test/Unit/lit.cfg.py
+++ b/test/Unit/lit.cfg.py
+@@ -3,6 +3,7 @@
+ # Configuration file for the 'lit' test runner.
+ 
+ import os
+import platform
+ import subprocess
+ 
+ import lit.formats
+@@ -55,3 +56,26 @@ if sys.platform in ["win32", "cygwin"] and os.path.isdir(config.shlibdir):
+ # Win32 may use %SYSTEMDRIVE% during file system shell operations, so propogate.
+ if sys.platform == "win32" and "SYSTEMDRIVE" in os.environ:
+     config.environment["SYSTEMDRIVE"] = os.environ["SYSTEMDRIVE"]
+
+# Add the LLVM dynamic libs to the platform-specific loader search path env var:
+#
+# TODO: this is copied from `clang`'s `lit.cfg.py`; should unify..
+def find_shlibpath_var():
+    if platform.system() in ["Linux", "FreeBSD", "NetBSD", "OpenBSD", "SunOS"]:
+        yield "LD_LIBRARY_PATH"
+    elif platform.system() == "Darwin":
+        yield "DYLD_LIBRARY_PATH"
+    elif platform.system() == "Windows":
+        yield "PATH"
+    elif platform.system() == "AIX":
+        yield "LIBPATH"
+
+for shlibpath_var in find_shlibpath_var():
+    shlibpath = os.path.pathsep.join(
+        (config.shlibdir,
+         config.environment.get(shlibpath_var, '')))
+    config.environment[shlibpath_var] = shlibpath
+    break
+else:
+    lit_config.warning("unable to inject shared library path on '{}'"
+                       .format(platform.system()))
+diff --git a/test/lit.cfg.py b/test/lit.cfg.py
+index 75a38b4c5dad..856fc75c9d74 100644
+--- a/test/lit.cfg.py
+++ b/test/lit.cfg.py
+@@ -42,6 +42,26 @@ llvm_config.with_environment("PATH", config.llvm_tools_dir, append_path=True)
+ llvm_config.with_system_environment(
+     ["HOME", "INCLUDE", "LIB", "TMP", "TEMP"])
+ 
+# Add the LLVM dynamic libs to the platform-specific loader search path env var:
+#
+# TODO: this is copied from `clang`'s `lit.cfg.py`; should unify..
+def find_shlibpath_var():
+    if platform.system() in ["Linux", "FreeBSD", "NetBSD", "OpenBSD", "SunOS"]:
+        yield "LD_LIBRARY_PATH"
+    elif platform.system() == "Darwin":
+        yield "DYLD_LIBRARY_PATH"
+    elif platform.system() == "Windows":
+        yield "PATH"
+    elif platform.system() == "AIX":
+        yield "LIBPATH"
+
+for shlibpath_var in find_shlibpath_var():
+    shlibpath = config.llvm_shlib_dir
+    llvm_config.with_environment(shlibpath_var, shlibpath, append_path = True)
+    break
+else:
+    lit_config.warning("unable to inject shared library path on '{}'"
+                       .format(platform.system()))
+ 
+ # Set up OCAMLPATH to include newly built OCaml libraries.
+ top_ocaml_lib = os.path.join(config.llvm_lib_dir, "ocaml")
+@@ -318,7 +338,7 @@ def have_cxx_shared_library():
+ 
+     try:
+         readobj_cmd = subprocess.Popen(
+-            [readobj_exe, "--needed-libs", readobj_exe], stdout=subprocess.PIPE
+            [readobj_exe, "--needed-libs", readobj_exe], stdout=subprocess.PIPE, env=config.environment
+         )
+     except OSError:
+         print("could not exec llvm-readobj")
+
--- a/pkgs/development/compilers/llvm/18/llvm/polly-lit-cfg-add-libs-to-dylib-path.patch
+++ b/pkgs/development/compilers/llvm/18/llvm/polly-lit-cfg-add-libs-to-dylib-path.patch
@ -0,0 +1,24 @@
+diff --git a/tools/polly/test/lit.cfg b/tools/polly/test/lit.cfg
+index 41e3a589c61e..09f3b17498b0 100644
+--- a/tools/polly/test/lit.cfg
+++ b/tools/polly/test/lit.cfg
+@@ -36,9 +36,17 @@ base_paths = [config.llvm_tools_dir, config.environment['PATH']]
+ path = os.path.pathsep.join(base_paths + config.extra_paths)
+ config.environment['PATH'] = path
+ 
+# (Copied from polly/test/Unit/lit.cfg)
+if platform.system() == 'Darwin':
+    shlibpath_var = 'DYLD_LIBRARY_PATH'
+elif platform.system() == 'Windows':
+    shlibpath_var = 'PATH'
+else:
+    shlibpath_var = 'LD_LIBRARY_PATH'
+
+ path = os.path.pathsep.join((config.llvm_libs_dir,
+-                              config.environment.get('LD_LIBRARY_PATH','')))
+-config.environment['LD_LIBRARY_PATH'] = path
+                              config.environment.get(shlibpath_var,'')))
+config.environment[shlibpath_var] = path
+ 
+ llvm_config.use_default_substitutions()
+ 
--- a/pkgs/development/compilers/llvm/18/openmp/default.nix
+++ b/pkgs/development/compilers/llvm/18/openmp/default.nix
@ -0,0 +1,73 @@
+{ lib
+, stdenv
+, llvm_meta
+, monorepoSrc
+, runCommand
+, cmake
+, ninja
+, llvm
+, targetLlvm
+, lit
+, clang-unwrapped
+, perl
+, pkg-config
+, xcbuild
+, version
+}:
+
+stdenv.mkDerivation rec {
+  pname = "openmp";
+  inherit version;
+
+  src = runCommand "${pname}-src-${version}" {} ''
+    mkdir -p "$out"
+    cp -r ${monorepoSrc}/cmake "$out"
+    cp -r ${monorepoSrc}/${pname} "$out"
+  '';
+
+  sourceRoot = "${src.name}/${pname}";
+
+  patches = [
+    ./fix-find-tool.patch
+    ./run-lit-directly.patch
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [ cmake ninja perl pkg-config lit ];
+  buildInputs = [
+    (if stdenv.buildPlatform == stdenv.hostPlatform then llvm else targetLlvm)
+  ];
+
+  nativeCheckInputs = lib.optional stdenv.hostPlatform.isDarwin xcbuild.xcrun;
+
+  # Unsup:Pass:XFail:Fail
+  # 26:267:16:8
+  doCheck = false;
+  checkTarget = "check-openmp";
+
+  preCheck = ''
+    patchShebangs ../tools/archer/tests/deflake.bash
+  '';
+
+  cmakeFlags = [
+    "-DCLANG_TOOL=${clang-unwrapped}/bin/clang"
+    "-DOPT_TOOL=${llvm}/bin/opt"
+    "-DLINK_TOOL=${llvm}/bin/llvm-link"
+  ];
+
+  meta = llvm_meta // {
+    homepage = "https://openmp.llvm.org/";
+    description = "Support for the OpenMP language";
+    longDescription = ''
+      The OpenMP subproject of LLVM contains the components required to build an
+      executable OpenMP program that are outside the compiler itself.
+      Contains the code for the runtime library against which code compiled by
+      "clang -fopenmp" must be linked before it can run and the library that
+      supports offload to target devices.
+    '';
+    # "All of the code is dual licensed under the MIT license and the UIUC
+    # License (a BSD-like license)":
+    license = with lib.licenses; [ mit ncsa ];
+  };
+}
--- a/pkgs/development/compilers/llvm/18/openmp/fix-find-tool.patch
+++ b/pkgs/development/compilers/llvm/18/openmp/fix-find-tool.patch
@ -0,0 +1,17 @@
+diff --git a/libomptarget/DeviceRTL/CMakeLists.txt b/libomptarget/DeviceRTL/CMakeLists.txt
+index 630947abec7e..9f032dc7bd3f 100644
+--- a/libomptarget/DeviceRTL/CMakeLists.txt
+++ b/libomptarget/DeviceRTL/CMakeLists.txt
+@@ -27,10 +27,10 @@ endif()
+ if (LLVM_DIR)
+   # Builds that use pre-installed LLVM have LLVM_DIR set.
+   # A standalone or LLVM_ENABLE_RUNTIMES=openmp build takes this route
+-  find_program(CLANG_TOOL clang PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
+  find_program(CLANG_TOOL clang PATHS ${LLVM_TOOLS_BINARY_DIR})
+   find_program(PACKAGER_TOOL clang-offload-packager PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
+   find_program(LINK_TOOL llvm-link PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
+-  find_program(OPT_TOOL opt PATHS ${LLVM_TOOLS_BINARY_DIR} NO_DEFAULT_PATH)
+  find_program(OPT_TOOL opt PATHS ${LLVM_TOOLS_BINARY_DIR})
+   if ((NOT CLANG_TOOL) OR (NOT LINK_TOOL) OR (NOT OPT_TOOL) OR (NOT PACKAGER_TOOL))
+     libomptarget_say("Not building DeviceRTL. Missing clang: ${CLANG_TOOL}, llvm-link: ${LINK_TOOL}, opt: ${OPT_TOOL}, or clang-offload-packager: ${PACKAGER_TOOL}")
+     return()
--- a/pkgs/development/compilers/llvm/18/openmp/run-lit-directly.patch
+++ b/pkgs/development/compilers/llvm/18/openmp/run-lit-directly.patch
--- a/pkgs/development/compilers/llvm/git/clang/default.nix
+++ b/pkgs/development/compilers/llvm/git/clang/default.nix
@ -70,9 +70,6 @@ let
    postInstall = ''
      ln -sv $out/bin/clang $out/bin/cpp

-      mkdir -p $lib/lib/clang
-      mv $lib/lib/${lib.versions.major version} $lib/lib/clang/${lib.versions.major version}
-
      # Move libclang to 'lib' output
      moveToOutput "lib/libclang.*" "$lib"
      moveToOutput "lib/libclang-cpp.*" "$lib"
--- a/pkgs/development/compilers/llvm/git/clang/gnu-install-dirs.patch
+++ b/pkgs/development/compilers/llvm/git/clang/gnu-install-dirs.patch
@ -1,30 +1,3 @@
-diff --git a/CMakeLists.txt b/CMakeLists.txt
-index f7936d72e088..a362fa49b534 100644
--- a/CMakeLists.txt
-+++ b/CMakeLists.txt
-@@ -31,7 +31,21 @@ if(CLANG_BUILT_STANDALONE)
-   find_package(LLVM REQUIRED HINTS "${LLVM_CMAKE_DIR}")
-   list(APPEND CMAKE_MODULE_PATH "${LLVM_DIR}")
- 
-  # Turn into CACHE PATHs for overwritting
-+  # We can't check LLVM_CONFIG here, because find_package(LLVM ...) also sets
-+  # LLVM_CONFIG.
-+  if (NOT LLVM_CONFIG_FOUND)
-+    # Pull values from LLVMConfig.cmake.  We can drop this once the llvm-config
-+    # path is removed.
-+    set(INCLUDE_DIRS ${LLVM_INCLUDE_DIRS})
-+    set(LLVM_OBJ_DIR "${LLVM_BINARY_DIR}")
-+    # N.B. this is just a default value, the CACHE PATHs below can be overriden.
-+    set(MAIN_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../llvm")
-+    set(TOOLS_BINARY_DIR "${LLVM_TOOLS_BINARY_DIR}")
-+    set(LIBRARY_DIR "${LLVM_LIBRARY_DIR}")
-+  else()
-+    set(INCLUDE_DIRS "${LLVM_BINARY_DIR}/include" "${MAIN_INCLUDE_DIR}")
-+  endif()
-+
-   set(LLVM_INCLUDE_DIRS ${LLVM_INCLUDE_DIRS} CACHE PATH "Path to llvm/include and any other header dirs needed")
-   set(LLVM_BINARY_DIR "${LLVM_BINARY_DIR}" CACHE PATH "Path to LLVM build tree")
-   set(LLVM_MAIN_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../llvm" CACHE PATH "Path to LLVM source tree")
 diff --git a/cmake/modules/AddClang.cmake b/cmake/modules/AddClang.cmake
 index 75b0080f6715..c895b884cd27 100644
 --- a/cmake/modules/AddClang.cmake
@ -48,7 +21,7 @@ index f2b0c5cddcbb..52f37fc368ce 100644
 add_header_target("utility-resource-headers" ${utility_files})
 
 get_clang_resource_dir(header_install_dir SUBDIR include)
-+set(header_install_dir ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/${CLANG_VERSION_MAJOR}/include)
+set(header_install_dir ${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}/clang/${CLANG_VERSION_MAJOR}/include)
 
 #############################################################
 # Install rules for the catch-all clang-resource-headers target
--- a/pkgs/development/compilers/llvm/git/compiler-rt/default.nix
+++ b/pkgs/development/compilers/llvm/git/compiler-rt/default.nix
@ -87,12 +87,9 @@ stdenv.mkDerivation {

  patches = [
    ./X86-support-extension.patch # Add support for i486 i586 i686 by reusing i386 config
-    ./gnu-install-dirs.patch
    # ld-wrapper dislikes `-rpath-link //nix/store`, so we normalize away the
    # extra `/`.
    ./normalize-var.patch
-    # Prevent a compilation error on darwin
-    ./darwin-targetconditionals.patch
    # See: https://github.com/NixOS/nixpkgs/pull/186575
    ../../common/compiler-rt/darwin-plistbuddy-workaround.patch
    # See: https://github.com/NixOS/nixpkgs/pull/194634#discussion_r999829893
@ -111,6 +108,8 @@ stdenv.mkDerivation {
    substituteInPlace cmake/config-ix.cmake \
      --replace 'set(COMPILER_RT_HAS_TSAN TRUE)' 'set(COMPILER_RT_HAS_TSAN FALSE)'
  '' + lib.optionalString (useLLVM && !haveLibc) ''
+    substituteInPlace lib/builtins/aarch64/sme-libc-routines.c \
+      --replace "<stdlib.h>" "<stddef.h>"
    substituteInPlace lib/builtins/int_util.c \
      --replace "#include <stdlib.h>" ""
    substituteInPlace lib/builtins/clear_cache.c \
--- a/pkgs/development/compilers/llvm/git/compiler-rt/gnu-install-dirs.patch
+++ b/pkgs/development/compilers/llvm/git/compiler-rt/gnu-install-dirs.patch
@ -1,20 +0,0 @@
-diff --git a/cmake/base-config-ix.cmake b/cmake/base-config-ix.cmake
-index 8a6219568b3f..30ee68a47ccf 100644
--- a/cmake/base-config-ix.cmake
-+++ b/cmake/base-config-ix.cmake
-@@ -100,13 +100,13 @@ endif()
- if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
-   set(COMPILER_RT_OUTPUT_LIBRARY_DIR
-     ${COMPILER_RT_OUTPUT_DIR}/lib)
-  extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" lib)
-+  extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" "${CMAKE_INSTALL_LIBDIR}")
-   set(COMPILER_RT_INSTALL_LIBRARY_DIR "${default_install_path}" CACHE PATH
-     "Path where built compiler-rt libraries should be installed.")
- else(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR AND NOT APPLE)
-   set(COMPILER_RT_OUTPUT_LIBRARY_DIR
-     ${COMPILER_RT_OUTPUT_DIR}/lib/${COMPILER_RT_OS_DIR})
-  extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" "lib/${COMPILER_RT_OS_DIR}")
-+  extend_path(default_install_path "${COMPILER_RT_INSTALL_PATH}" "${CMAKE_INSTALL_LIBDIR}/${COMPILER_RT_OS_DIR}")
-   set(COMPILER_RT_INSTALL_LIBRARY_DIR "${default_install_path}" CACHE PATH
-     "Path where built compiler-rt libraries should be installed.")
- endif()
--- a/pkgs/development/compilers/llvm/git/default.nix
+++ b/pkgs/development/compilers/llvm/git/default.nix
@ -17,15 +17,20 @@
    else pkgs.bintools
 , darwin
 # LLVM release information; specify one of these but not both:
-, gitRelease ? null
+, gitRelease ? {
+    version = "19.0.0-git";
+    rev = "65058a8d732c3c41664a4dad1a1ae2a504d5c98e";
+    rev-version = "19.0.0-unstable-2024-03-16";
+    sha256 = "sha256-xV33kx/8OZ2KLtaz25RmudDrlIX7nScauTykf87jyTE=";
+}
  # i.e.:
  # {
  #   version = /* i.e. "15.0.0" */;
  #   rev = /* commit SHA */;
-  #   rev-version = /* human readable version; i.e. "unstable-2022-26-07" */;
+  #   rev-version = /* human readable version; i.e. "15.0.0-unstable-2022-07-26" */;
  #   sha256 = /* checksum for this release, can omit if specifying your own `monorepoSrc` */;
  # }
-, officialRelease ? { version = "18.1.0-rc4"; sha256 = "sha256-fVpwewbjoPMPslIEZ+WAtaQ+YKc0XWGl8EbP/TbQb8o="; }
+, officialRelease ? null
  # i.e.:
  # {
  #   version = /* i.e. "15.0.0" */;
--- a/pkgs/development/compilers/llvm/git/libcxx/default.nix
+++ b/pkgs/development/compilers/llvm/git/libcxx/default.nix
@ -1,5 +1,5 @@
 { lib, stdenv, llvm_meta
-, monorepoSrc, runCommand, fetchpatch
+, monorepoSrc, runCommand
 , cmake, lndir, ninja, python3, fixDarwinDylibNames, version
 , cxxabi ? if stdenv.hostPlatform.isFreeBSD then libcxxrt else null
 , libcxxrt, libunwind
@ -19,11 +19,11 @@ let
  # Note: useLLVM is likely false for Darwin but true under pkgsLLVM
  useLLVM = stdenv.hostPlatform.useLLVM or false;

-  cxxabiCMakeFlags = lib.optionals (useLLVM && !stdenv.hostPlatform.isWasm) [
-    "-DLIBCXXABI_USE_COMPILER_RT=ON"
-    "-DLIBCXXABI_USE_LLVM_UNWINDER=ON"
-  ] ++ lib.optionals (lib.versionAtLeast version "18" && !(useLLVM && !stdenv.hostPlatform.isWasm)) [
+  cxxabiCMakeFlags = [
    "-DLIBCXXABI_USE_LLVM_UNWINDER=OFF"
+  ] ++ lib.optionals (useLLVM && !stdenv.hostPlatform.isWasm) [
+    "-DLIBCXXABI_ADDITIONAL_LIBRARIES=unwind"
+    "-DLIBCXXABI_USE_COMPILER_RT=ON"
  ] ++ lib.optionals stdenv.hostPlatform.isWasm [
    "-DLIBCXXABI_ENABLE_THREADS=OFF"
    "-DLIBCXXABI_ENABLE_EXCEPTIONS=OFF"
@ -87,18 +87,6 @@ stdenv.mkDerivation rec {
  patches = lib.optionals (stdenv.isDarwin && lib.versionOlder stdenv.hostPlatform.darwinMinVersion "10.13") [
    # https://github.com/llvm/llvm-project/issues/64226
    ./0001-darwin-10.12-mbstate_t-fix.patch
-  ] ++ lib.optionals (cxxabi == null && lib.versionAtLeast version "18") [
-    # Allow building libcxxabi alone when using LLVM unwinder
-    (fetchpatch {
-      url = "https://github.com/llvm/llvm-project/commit/77610dd10454e87bb387040d2b51100a17ac5755.patch";
-      revert = true;
-      hash = "sha256-jFbC3vBY3nKfjknJ7UzaPyoy0iSYdD3+jUmOFeOaVcA=";
-    })
-    (fetchpatch {
-      url = "https://github.com/llvm/llvm-project/commit/48e5b5ea92674ded69b998cf35724d9012c0f57d.patch";
-      revert = true;
-      hash = "sha256-WN63L4T3GxVozPZb6kx21AgNe4rwwSUOeeryIGsvQYY=";
-    })
  ];

  postPatch = ''
--- a/pkgs/development/compilers/llvm/git/libunwind/default.nix
+++ b/pkgs/development/compilers/llvm/git/libunwind/default.nix
@ -27,15 +27,6 @@ stdenv.mkDerivation rec {

  sourceRoot = "${src.name}/runtimes";

-  prePatch = ''
-    cd ../${pname}
-    chmod -R u+w .
-  '';
-
-  postPatch = ''
-    cd ../runtimes
-  '';
-
  postInstall = lib.optionalString (enableShared && !stdenv.hostPlatform.isDarwin) ''
    # libcxxabi wants to link to libunwind_shared.so (?).
    ln -s $out/lib/libunwind.so $out/lib/libunwind_shared.so
--- a/pkgs/development/compilers/llvm/git/lld/default.nix
+++ b/pkgs/development/compilers/llvm/git/lld/default.nix
@ -24,13 +24,13 @@ stdenv.mkDerivation rec {

  sourceRoot = "${src.name}/${pname}";

+  nativeBuildInputs = [ cmake ninja ];
+  buildInputs = [ libllvm libxml2 ];
+
  patches = [
    ./gnu-install-dirs.patch
  ];

-  nativeBuildInputs = [ cmake ninja ];
-  buildInputs = [ libllvm libxml2 ];
-
  cmakeFlags = [
    "-DLLD_INSTALL_PACKAGE_DIR=${placeholder "dev"}/lib/cmake/lld"
  ] ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
--- a/pkgs/development/compilers/llvm/git/lld/gnu-install-dirs.patch
+++ b/pkgs/development/compilers/llvm/git/lld/gnu-install-dirs.patch
@ -1,34 +1,3 @@
-diff --git a/CMakeLists.txt b/CMakeLists.txt
-index 3d6225646fe6..9b5d0b15af13 100644
--- a/CMakeLists.txt
-+++ b/CMakeLists.txt
-@@ -33,10 +33,22 @@ if(LLD_BUILT_STANDALONE)
-   find_package(LLVM REQUIRED HINTS "${LLVM_CMAKE_DIR}")
-   list(APPEND CMAKE_MODULE_PATH "${LLVM_DIR}")
- 
-  # Turn into CACHE PATHs for overwriting
-  set(LLVM_INCLUDE_DIRS ${LLVM_INCLUDE_DIRS} CACHE PATH "Path to llvm/include and any other header dirs needed")
-  set(LLVM_BINARY_DIR "${LLVM_BINARY_DIR}" CACHE PATH "Path to LLVM build tree")
-  set(LLVM_MAIN_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../llvm" CACHE PATH "Path to LLVM source tree")
-+  # We can't check LLVM_CONFIG here, because find_package(LLVM ...) also sets
-+  # LLVM_CONFIG.
-+  if (NOT LLVM_CONFIG_FOUND)
-+    # Pull values from LLVMConfig.cmake.  We can drop this once the llvm-config
-+    # path is removed.
-+    set(INCLUDE_DIRS ${LLVM_INCLUDE_DIRS})
-+    set(LLVM_OBJ_DIR "${LLVM_BINARY_DIR}")
-+    # N.B. this is just a default value, the CACHE PATHs below can be overridden.
-+    set(MAIN_SRC_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../llvm")
-+  else()
-+    set(INCLUDE_DIRS "${LLVM_BINARY_DIR}/include" "${MAIN_INCLUDE_DIR}")
-+  endif()
-+
-+  set(LLVM_INCLUDE_DIRS ${INCLUDE_DIRS} CACHE PATH "Path to llvm/include and any other header dirs needed")
-+  set(LLVM_BINARY_DIR "${LLVM_OBJ_ROOT}" CACHE PATH "Path to LLVM build tree")
-+  set(LLVM_MAIN_SRC_DIR "${MAIN_SRC_DIR}" CACHE PATH "Path to LLVM source tree")
- 
-   find_program(LLVM_TABLEGEN_EXE "llvm-tblgen" ${LLVM_TOOLS_BINARY_DIR}
-     NO_DEFAULT_PATH)
 diff --git a/cmake/modules/AddLLD.cmake b/cmake/modules/AddLLD.cmake
 index d3924f7243d4..42a7cd62281c 100644
 --- a/cmake/modules/AddLLD.cmake
--- a/pkgs/development/compilers/llvm/git/llvm/default.nix
+++ b/pkgs/development/compilers/llvm/git/llvm/default.nix
@ -179,6 +179,10 @@ stdenv.mkDerivation (rec {
    substituteInPlace test/ExecutionEngine/Interpreter/intrinsics.ll \
      --replace "%roundeven32 = call float @llvm.roundeven.f32(float 0.000000e+00)" "" \
      --replace "%roundeven64 = call double @llvm.roundeven.f64(double 0.000000e+00)" ""
+
+    # fails when run in sandbox
+    substituteInPlace unittests/Support/VirtualFileSystemTest.cpp \
+      --replace "PhysicalFileSystemWorkingDirFailure" "DISABLED_PhysicalFileSystemWorkingDirFailure"
  '' + optionalString (stdenv.isDarwin && stdenv.hostPlatform.isx86) ''
    # This test fails on darwin x86_64 because `sw_vers` reports a different
    # macOS version than what LLVM finds by reading
@ -382,7 +386,6 @@ stdenv.mkDerivation (rec {
      --replace 'set(LLVM_BINARY_DIR "''${LLVM_INSTALL_PREFIX}")' 'set(LLVM_BINARY_DIR "'"$lib"'")'
  ''
  + optionalString (stdenv.isDarwin && enableSharedLibraries) ''
-    ln -s $lib/lib/libLLVM.dylib $lib/lib/libLLVM-${shortVersion}.dylib
    ln -s $lib/lib/libLLVM.dylib $lib/lib/libLLVM-${release_version}.dylib
  ''
  + optionalString (stdenv.buildPlatform != stdenv.hostPlatform) ''
--- a/pkgs/development/compilers/llvm/git/llvm/gnu-install-dirs-polly.patch
+++ b/pkgs/development/compilers/llvm/git/llvm/gnu-install-dirs-polly.patch
@ -1,12 +1,6 @@
-This is the one remaining Polly install dirs related change that hasn't made it
-into upstream yet; previously this patch file also included:
-https://reviews.llvm.org/D117541
-
-diff --git a/tools/polly/cmake/polly_macros.cmake b/tools/polly/cmake/polly_macros.cmake
-index 518a09b45a42..bd9d6f5542ad 100644
--- a/tools/polly/cmake/polly_macros.cmake
-+++ b/tools/polly/cmake/polly_macros.cmake
-@@ -45,8 +45,8 @@ macro(add_polly_library name)
+--- a/tools/polly/cmake/polly_macros.cmake	2024-03-15 17:36:20.550893344 -0700
+++ b/tools/polly/cmake/polly_macros.cmake	2024-03-15 17:37:06.277332960 -0700
+@@ -45,8 +45,8 @@
     install(TARGETS ${name}
       COMPONENT ${name}
       EXPORT LLVMExports
--- a/pkgs/development/compilers/llvm/git/llvm/gnu-install-dirs.patch
+++ b/pkgs/development/compilers/llvm/git/llvm/gnu-install-dirs.patch
@ -40,7 +40,7 @@ index 230620c37027..dd16cab1835e 100644
   if (APPLE)
     set(_install_name_dir INSTALL_NAME_DIR "@rpath")
 -    set(_install_rpath "@loader_path/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
-+    set(_install_rpath "@loader_path/../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+    set(_install_rpath ${extra_libdir})
   elseif(${CMAKE_SYSTEM_NAME} MATCHES "AIX" AND BUILD_SHARED_LIBS)
     # $ORIGIN is not interpreted at link time by aix ld.
     # Since BUILD_SHARED_LIBS is only recommended for use by developers,
@ -72,8 +72,8 @@ index 230620c37027..dd16cab1835e 100644
 +    # As noted in the differential above, an alternative solution is to have
 +    # all rdeps of nixpkgs' LLVM (that use the AddLLVM.cmake machinery) set
 +    # `CMAKE_INSTALL_RPATH`.
-+    set(_build_rpath "\$ORIGIN/../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
-+    set(_install_rpath "\$ORIGIN/../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+    set(_build_rpath "\$ORIGIN/../lib${LLVM_LIBDIR_SUFFIX}" ${extra_libdir})
+    set(_install_rpath ${extra_libdir})
     if(${CMAKE_SYSTEM_NAME} MATCHES "(FreeBSD|DragonFly)")
       set_property(TARGET ${name} APPEND_STRING PROPERTY
                    LINK_FLAGS " -Wl,-z,origin ")
@ -86,10 +86,10 @@ index 891c9e6d618c..8d963f3b0069 100644
 
   if( APPLE )
 -    set(ocaml_rpath "@executable_path/../../../lib${LLVM_LIBDIR_SUFFIX}")
-+    set(ocaml_rpath "@executable_path/../../../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}")
+    set(ocaml_rpath ${LLVM_LIBRARY_DIR})
   elseif( UNIX )
 -    set(ocaml_rpath "\\$ORIGIN/../../../lib${LLVM_LIBDIR_SUFFIX}")
-+    set(ocaml_rpath "\\$ORIGIN/../../../${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}")
+    set(ocaml_rpath ${LLVM_LIBRARY_DIR})
   endif()
   list(APPEND ocaml_flags "-ldopt" "-Wl,-rpath,${ocaml_rpath}")
 
--- a/pkgs/development/compilers/llvm/git/llvm/lit-shell-script-runner-set-dyld-library-path.patch
+++ b/pkgs/development/compilers/llvm/git/llvm/lit-shell-script-runner-set-dyld-library-path.patch
@ -1,17 +1,12 @@
-diff --git a/utils/lit/lit/TestRunner.py b/utils/lit/lit/TestRunner.py
-index 0242e0b75af3..d732011306f7 100644
--- a/utils/lit/lit/TestRunner.py
-+++ b/utils/lit/lit/TestRunner.py
-@@ -1029,6 +1029,12 @@ def executeScript(test, litConfig, tmpBase, commands, cwd):
-             f.write('@echo off\n')
-         f.write('\n@if %ERRORLEVEL% NEQ 0 EXIT\n'.join(commands))
+--- a/utils/lit/lit/TestRunner.py	2024-03-15 17:27:53.170780798 -0700
+++ b/utils/lit/lit/TestRunner.py	2024-03-15 17:28:43.277447791 -0700
+@@ -1183,6 +1183,9 @@
+         f.write("@echo on\n")
+         f.write("\n@if %ERRORLEVEL% NEQ 0 EXIT\n".join(commands))
     else:
-+        # This env var is *purged* when invoking subprocesses so we have to
-+        # manually set it from within the bash script in order for the commands
-+        # in run lines to see this var:
 +        if "DYLD_LIBRARY_PATH" in test.config.environment:
 +            f.write(f'export DYLD_LIBRARY_PATH="{test.config.environment["DYLD_LIBRARY_PATH"]}"\n')
 +
         for i, ln in enumerate(commands):
-             match = re.match(kPdbgRegex, ln)
+             match = re.fullmatch(kPdbgRegex, ln)
             if match:
--- a/pkgs/development/compilers/llvm/git/openmp/default.nix
+++ b/pkgs/development/compilers/llvm/git/openmp/default.nix
@ -29,7 +29,6 @@ stdenv.mkDerivation rec {

  patches = [
    ./fix-find-tool.patch
-    ./gnu-install-dirs.patch
    ./run-lit-directly.patch
  ];

--- a/pkgs/development/compilers/llvm/git/openmp/gnu-install-dirs.patch
+++ b/pkgs/development/compilers/llvm/git/openmp/gnu-install-dirs.patch
@ -1,22 +0,0 @@
-diff --git a/CMakeLists.txt b/CMakeLists.txt
-index b6ddbe90516d..311ab1d50e7f 100644
--- a/CMakeLists.txt
-+++ b/CMakeLists.txt
-@@ -29,7 +29,7 @@ if (OPENMP_STANDALONE_BUILD)
-   set(OPENMP_LIBDIR_SUFFIX "" CACHE STRING
-     "Suffix of lib installation directory, e.g. 64 => lib64")
-   # Do not use OPENMP_LIBDIR_SUFFIX directly, use OPENMP_INSTALL_LIBDIR.
-  set(OPENMP_INSTALL_LIBDIR "lib${OPENMP_LIBDIR_SUFFIX}" CACHE STRING
-+  set(OPENMP_INSTALL_LIBDIR "${CMAKE_INSTALL_LIBDIR}${OPENMP_LIBDIR_SUFFIX}" CACHE STRING
-       "Path where built OpenMP libraries should be installed.")
- 
-   # Group test settings.
-@@ -47,7 +47,7 @@ if (OPENMP_STANDALONE_BUILD)
- else()
-   set(OPENMP_ENABLE_WERROR ${LLVM_ENABLE_WERROR})
-   # If building in tree, we honor the same install suffix LLVM uses.
-  set(OPENMP_INSTALL_LIBDIR "lib${LLVM_LIBDIR_SUFFIX}" CACHE STRING
-+  set(OPENMP_INSTALL_LIBDIR "${CMAKE_INSTALL_LIBDIR}${LLVM_LIBDIR_SUFFIX}" CACHE STRING
-       "Path where built OpenMP libraries should be installed.")
- 
-   if (NOT MSVC)
--- a/pkgs/development/compilers/llvm/update-git.py
+++ b/pkgs/development/compilers/llvm/update-git.py
@ -43,7 +43,7 @@ def get_current_revision():
    """Get the current revision of llvmPackages_git."""
    with open(DEFAULT_NIX) as f:
        for line in f:
-            rev = re.search(r'^  rev = "(.*)";', line)
+            rev = re.search(r'^    rev = "(.*)";', line)
            if rev:
                return rev.group(1)
    sys.exit(1)
@ -75,11 +75,11 @@ hash = nix_prefetch_url(f'https://github.com/llvm/llvm-project/archive/{commit["
 print('Updating default.nix...')
 with fileinput.FileInput(DEFAULT_NIX, inplace=True) as f:
    for line in f:
-        if match := re.search(r'^  rev-version = "unstable-(.+)";', line):
+        if match := re.search(r'^    rev-version = "unstable-(.+)";', line):
                old_date = match.group(1)
-        result = re.sub(r'^  release_version = ".+";', f'  release_version = "{release_version}";', line)
-        result = re.sub(r'^  rev = ".*";', f'  rev = "{commit["sha"]}";', result)
-        result = re.sub(r'^  rev-version = ".+";', f'  rev-version = "{version}";', result)
+        result = re.sub(r'^    version = ".+";', f'    version = "{release_version}";', line)
+        result = re.sub(r'^    rev = ".*";', f'    rev = "{commit["sha"]}";', result)
+        result = re.sub(r'^    rev-version = ".+";', f'    rev-version = "{version}";', result)
        result = re.sub(r'^    sha256 = ".+";', f'    sha256 = "{hash}";', result)
        print(result, end='')
 # Commit the result:
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@ -16527,6 +16527,31 @@ with pkgs;
    targetLlvm = targetPackages.llvmPackages_17.llvm or llvmPackages_17.llvm;
  }));

+  inherit
+    (rec {
+      llvmPackages_18 = recurseIntoAttrs (callPackage ../development/compilers/llvm/18 ({
+        inherit (stdenvAdapters) overrideCC;
+        buildLlvmTools = buildPackages.llvmPackages_18.tools;
+        targetLlvmLibraries = targetPackages.llvmPackages_18.libraries or llvmPackages_18.libraries;
+        targetLlvm = targetPackages.llvmPackages_18.llvm or llvmPackages_18.llvm;
+      }));
+
+      clang_18 = llvmPackages_18.clang;
+      lld_18 = llvmPackages_18.lld;
+      lldb_18 = llvmPackages_18.lldb;
+      llvm_18 = llvmPackages_18.llvm;
+
+      clang-tools_18 = callPackage ../development/tools/clang-tools {
+        llvmPackages = llvmPackages_18;
+      };
+    })
+      llvmPackages_18
+      clang_18
+      lld_18
+      lldb_18
+      llvm_18
+      clang-tools_18;
+
  lorri = callPackage ../tools/misc/lorri {
    inherit (darwin.apple_sdk.frameworks) CoreServices Security;
  };