[clang] 6f2ee1c - [OpenMP][AMDGPU] Optimize the linked in math libraries

[Johannes Doerfert via cfe-commits]

Author: Johannes Doerfert
Date: 2022-01-19T23:36:36-06:00
New Revision: 6f2ee1ca5e39b4286f7eb1aeb63b408f952f93c9

URL: https://github.com/llvm/llvm-project/commit/6f2ee1ca5e39b4286f7eb1aeb63b408f952f93c9
DIFF: https://github.com/llvm/llvm-project/commit/6f2ee1ca5e39b4286f7eb1aeb63b408f952f93c9.diff

LOG: [OpenMP][AMDGPU] Optimize the linked in math libraries

Once we linked in math files, potentially even if we link in only other
"system libraries", we want to optimize the code again. This is not only
reasonable but also helps to hide various problems with the missing
attribute annotations in the math libraries.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D116906

Added: 
    

Modified: 
    clang/lib/Driver/ToolChains/AMDGPUOpenMP.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Driver/ToolChains/AMDGPUOpenMP.cpp b/clang/lib/Driver/ToolChains/AMDGPUOpenMP.cpp
index 983d40636b0cd..6899f9360da5d 100644
--- a/clang/lib/Driver/ToolChains/AMDGPUOpenMP.cpp
+++ b/clang/lib/Driver/ToolChains/AMDGPUOpenMP.cpp
@@ -16,6 +16,7 @@
 #include "clang/Driver/DriverDiagnostic.h"
 #include "clang/Driver/InputInfo.h"
 #include "clang/Driver/Options.h"
+#include "clang/Driver/Tool.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/FormatAdapters.h"
@@ -95,9 +96,9 @@ const char *AMDGCN::OpenMPLinker::constructLLVMLinkCommand(
     if (II.isFilename())
       CmdArgs.push_back(II.getFilename());
 
+  bool HasLibm = false;
   if (Args.hasArg(options::OPT_l)) {
     auto Lm = Args.getAllArgValues(options::OPT_l);
-    bool HasLibm = false;
     for (auto &Lib : Lm) {
       if (Lib == "m") {
         HasLibm = true;
@@ -143,6 +144,26 @@ const char *AMDGCN::OpenMPLinker::constructLLVMLinkCommand(
   C.addCommand(std::make_unique<Command>(
       JA, *this, ResponseFileSupport::AtFileCurCP(), Exec, CmdArgs, Inputs,
       InputInfo(&JA, Args.MakeArgString(OutputFileName))));
+
+  // If we linked in libm definitions late we run another round of optimizations
+  // to inline the definitions and fold what is foldable.
+  if (HasLibm) {
+    ArgStringList OptCmdArgs;
+    const char *OptOutputFileName =
+        getOutputFileName(C, OutputFilePrefix, "-linked-opt", "bc");
+    addLLCOptArg(Args, OptCmdArgs);
+    OptCmdArgs.push_back(OutputFileName);
+    OptCmdArgs.push_back("-o");
+    OptCmdArgs.push_back(OptOutputFileName);
+    const char *OptExec =
+        Args.MakeArgString(getToolChain().GetProgramPath("opt"));
+    C.addCommand(std::make_unique<Command>(
+        JA, *this, ResponseFileSupport::AtFileCurCP(), OptExec, OptCmdArgs,
+        InputInfo(&JA, Args.MakeArgString(OutputFileName)),
+        InputInfo(&JA, Args.MakeArgString(OptOutputFileName))));
+    OutputFileName = OptOutputFileName;
+  }
+
   return OutputFileName;
 }