Use lld linker for clangOmpss2 for LTO

bsc/llvm-ompss2/clang.nix

@@ -67,7 +67,7 @@ stdenv.mkDerivation rec {
       "-DCMAKE_CXX_FLAGS_DEBUG=-g -ggnu-pubnames"
       "-DCMAKE_EXE_LINKER_FLAGS_DEBUG=-Wl,-gdb-index"
       "-DLLVM_LIT_ARGS=-sv --xunit-xml-output=xunit.xml"
-      "-DLLVM_ENABLE_PROJECTS=clang;openmp;compiler-rt;flang"
+      "-DLLVM_ENABLE_PROJECTS=clang;openmp;compiler-rt;flang;lld"
       "-DLLVM_ENABLE_ASSERTIONS=${enableAssertions}"
       "-DLLVM_INSTALL_TOOLCHAIN_ONLY=ON"
       "-DCMAKE_INSTALL_BINDIR=bin"

bsc/llvm-ompss2/default.nix

@@ -4,14 +4,27 @@
 , nanos6
 , clangOmpss2Unwrapped
 , wrapCCWith
+, llvmPackages
 }:
 
 
 let
+
+  # We need to replace the lld linker from bintools with our linker just built,
+  # otherwise we run into incompatibility issues when mixing compiler and linker
+  # versions.
+  bintools-unwrapped = llvmPackages.tools.bintools-unwrapped.override {
+    lld = clangOmpss2Unwrapped;
+  };
+  bintools = llvmPackages.tools.bintools.override {
+    bintools = bintools-unwrapped;
+  };
+
   targetConfig = stdenv.targetPlatform.config;
   inherit gcc nanos6;
-in wrapCCWith rec {
   cc = clangOmpss2Unwrapped;
+in wrapCCWith {
+  inherit cc bintools;
   extraBuildCommands = ''
     echo "-target ${targetConfig}" >> $out/nix-support/cc-cflags
     echo "-B${gcc.cc}/lib/gcc/${targetConfig}/${gcc.version}" >> $out/nix-support/cc-cflags

overlay.nix

@@ -105,6 +105,7 @@ let
 
     clangOmpss2 = appendPasstru (
       callPackage ./bsc/llvm-ompss2/default.nix {
+        llvmPackages = self.llvmPackages_latest;
         clangOmpss2Unwrapped = bsc.clangOmpss2Unwrapped;
       }) { CC = "clang"; CXX = "clang++"; };
 
@@ -113,6 +114,11 @@ let
         clangOmpss2Unwrapped = bsc.clangOmpss2UnwrappedGit;
       }) { CC = "clang"; CXX = "clang++"; };
 
+    stdenvClangOmpss2 = self.stdenv.override {
+      cc = bsc.clangOmpss2;
+      allowedRequisites = null;
+    };
+
     mcxx = bsc.mcxxRelease;
     mcxxRelease = callPackage ./bsc/mcxx/default.nix { };
     mcxxGit = callPackage ./bsc/mcxx/git.nix { };
@@ -302,6 +308,7 @@ let
       compilers.hello-c = callPackage ./test/compilers/hello-c.nix { };
       compilers.hello-cpp = callPackage ./test/compilers/hello-cpp.nix { };
       compilers.hello-f = callPackage ./test/compilers/hello-f.nix { };
+      compilers.lto = callPackage ./test/compilers/lto.nix { };
       compilers.intel2023.icx.c = compilers.hello-c.override {
         stdenv = bsc.intel2023.stdenv;
       };
@@ -317,6 +324,9 @@ let
       compilers.intel2023.ifort = compilers.hello-f.override {
         stdenv = bsc.intel2023.stdenv-ifort;
       };
+      compilers.clangOmpss2.lto = compilers.lto.override {
+        stdenv = bsc.stdenvClangOmpss2;
+      };
     };
 
     testAll = with bsc.test; [
@@ -325,6 +335,7 @@ let
       compilers.intel2023.icx.cpp
       compilers.intel2023.icc.cpp
       compilers.intel2023.ifort
+      compilers.clangOmpss2.lto
     ];
 
     ci = import ./test/ci.nix {

test/compilers/lto.nix

@@ -0,0 +1,43 @@
+{ stdenv, writeText, which, strace }:
+
+let
+  hello_c = writeText "hello.c" ''
+    #include <stdio.h>
+    #include <limits.h>
+    #include <xmmintrin.h>
+
+    int main()
+    {
+            printf("Hello world!\n");
+            return 0;
+    }
+  '';
+in
+
+stdenv.mkDerivation rec {
+  version = "0.0.1";
+  name = "lto-c";
+  buildInputs = [ stdenv which strace ];
+  src = hello_c;
+  dontUnpack = true;
+  dontConfigure = true;
+  NIX_DEBUG = 0;
+  buildPhase = ''
+    set -x
+    echo CC=$CC
+    echo LD=$LD
+    echo -------------------------------------------
+    env
+    echo -------------------------------------------
+
+    cp ${hello_c} hello.c
+    $CC -v -flto hello.c -o hello
+    ./hello
+
+    set +x
+  '';
+
+  installPhase = ''
+    touch $out
+  '';
+}