[CodeGen] [CUDA] Add the ability set default attrs on functions in linked modules.

Summary:
Now when you ask clang to link in a bitcode module, you can tell it to
set attributes on that module's functions to match what we would have
set if we'd emitted those functions ourselves.

This is particularly important for fast-math attributes in CUDA
compilations.

Each CUDA compilation links in libdevice, a bitcode library provided by
nvidia as part of the CUDA distribution.  Without this patch, if we have
a user-function F that is compiled with -ffast-math that calls a
function G from libdevice, F will have the unsafe-fp-math=true (etc.)
attributes, but G will have no attributes.

Since F calls G, the inliner will merge G's attributes into F's.  It
considers the lack of an unsafe-fp-math=true attribute on G to be
tantamount to unsafe-fp-math=false, so it "merges" these by setting
unsafe-fp-math=false on F.

This then continues up the call graph, until every function that
(transitively) calls something in libdevice gets unsafe-fp-math=false
set, thus disabling fastmath in almost all CUDA code.

Reviewers: echristo

Subscribers: hfinkel, llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D28538

llvm-svn: 293097

1 files changed, 44 insertions, 40 deletions

diff --git a/clang/lib/CodeGen/CodeGenAction.cpp b/clang/lib/CodeGen/CodeGenAction.cpp
index 0daedf408c9..527d90e44c1 100644
--- a/clang/lib/CodeGen/CodeGenAction.cpp
+++ b/clang/lib/CodeGen/CodeGenAction.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/CodeGen/CodeGenAction.h"
+#include "CodeGenModule.h"
 #include "CoverageMappingGen.h"
 #include "clang/AST/ASTConsumer.h"
 #include "clang/AST/ASTContext.h"
@@ -16,7 +18,6 @@
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/CodeGen/BackendUtil.h"
-#include "clang/CodeGen/CodeGenAction.h"
 #include "clang/CodeGen/ModuleBuilder.h"
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/FrontendDiagnostic.h"
@@ -41,6 +42,8 @@ using namespace llvm;
 
 namespace clang {
   class BackendConsumer : public ASTConsumer {
+    using LinkModule = CodeGenAction::LinkModule;
+
     virtual void anchor();
     DiagnosticsEngine &Diags;
     BackendAction Action;
@@ -61,43 +64,37 @@ namespace clang {
 
     std::unique_ptr<CodeGenerator> Gen;
 
-    SmallVector<std::pair<unsigned, std::unique_ptr<llvm::Module>>, 4>
-        LinkModules;
+    SmallVector<LinkModule, 4> LinkModules;
 
     // This is here so that the diagnostic printer knows the module a diagnostic
     // refers to.
     llvm::Module *CurLinkModule = nullptr;
 
   public:
-    BackendConsumer(
-        BackendAction Action, DiagnosticsEngine &Diags,
-        const HeaderSearchOptions &HeaderSearchOpts,
-        const PreprocessorOptions &PPOpts, const CodeGenOptions &CodeGenOpts,
-        const TargetOptions &TargetOpts, const LangOptions &LangOpts,
-        bool TimePasses, const std::string &InFile,
-        const SmallVectorImpl<std::pair<unsigned, llvm::Module *>> &LinkModules,
-        std::unique_ptr<raw_pwrite_stream> OS, LLVMContext &C,
-        CoverageSourceInfo *CoverageInfo = nullptr)
+    BackendConsumer(BackendAction Action, DiagnosticsEngine &Diags,
+                    const HeaderSearchOptions &HeaderSearchOpts,
+                    const PreprocessorOptions &PPOpts,
+                    const CodeGenOptions &CodeGenOpts,
+                    const TargetOptions &TargetOpts,
+                    const LangOptions &LangOpts, bool TimePasses,
+                    const std::string &InFile,
+                    SmallVector<LinkModule, 4> LinkModules,
+                    std::unique_ptr<raw_pwrite_stream> OS, LLVMContext &C,
+                    CoverageSourceInfo *CoverageInfo = nullptr)
         : Diags(Diags), Action(Action), HeaderSearchOpts(HeaderSearchOpts),
           CodeGenOpts(CodeGenOpts), TargetOpts(TargetOpts), LangOpts(LangOpts),
           AsmOutStream(std::move(OS)), Context(nullptr),
           LLVMIRGeneration("irgen", "LLVM IR Generation Time"),
           LLVMIRGenerationRefCount(0),
           Gen(CreateLLVMCodeGen(Diags, InFile, HeaderSearchOpts, PPOpts,
-                                CodeGenOpts, C, CoverageInfo)) {
+                                CodeGenOpts, C, CoverageInfo)),
+          LinkModules(std::move(LinkModules)) {
       llvm::TimePassesIsEnabled = TimePasses;
-      for (auto &I : LinkModules)
-        this->LinkModules.push_back(
-            std::make_pair(I.first, std::unique_ptr<llvm::Module>(I.second)));
     }
     llvm::Module *getModule() const { return Gen->GetModule(); }
     std::unique_ptr<llvm::Module> takeModule() {
       return std::unique_ptr<llvm::Module>(Gen->ReleaseModule());
     }
-    void releaseLinkModules() {
-      for (auto &I : LinkModules)
-        I.second.release();
-    }
 
     void HandleCXXStaticMemberVarInstantiation(VarDecl *VD) override {
       Gen->HandleCXXStaticMemberVarInstantiation(VD);
@@ -159,6 +156,21 @@ namespace clang {
         HandleTopLevelDecl(D);
     }
 
+    // Links each entry in LinkModules into our module.  Returns true on error.
+    bool LinkInModules() {
+      for (auto &LM : LinkModules) {
+        if (LM.PropagateAttrs)
+          for (Function &F : *LM.Module)
+            Gen->CGM().AddDefaultFnAttrs(F);
+
+        CurLinkModule = LM.Module.get();
+        if (Linker::linkModules(*getModule(), std::move(LM.Module),
+                                LM.LinkFlags))
+          return true;
+      }
+      return false; // success
+    }
+
     void HandleTranslationUnit(ASTContext &C) override {
       {
         PrettyStackTraceString CrashInfo("Per-file LLVM IR generation");
@@ -216,13 +228,9 @@ namespace clang {
           Ctx.setDiagnosticHotnessRequested(true);
       }
 
-      // Link LinkModule into this module if present, preserving its validity.
-      for (auto &I : LinkModules) {
-        unsigned LinkFlags = I.first;
-        CurLinkModule = I.second.get();
-        if (Linker::linkModules(*getModule(), std::move(I.second), LinkFlags))
-          return;
-      }
+      // Link each LinkModule into our module.
+      if (LinkInModules())
+        return;
 
       EmbedBitcode(getModule(), CodeGenOpts, llvm::MemoryBufferRef());
 
@@ -729,10 +737,6 @@ void CodeGenAction::EndSourceFileAction() {
   if (!getCompilerInstance().hasASTConsumer())
     return;
 
-  // Take back ownership of link modules we passed to consumer.
-  if (!LinkModules.empty())
-    BEConsumer->releaseLinkModules();
-
   // Steal the module from the consumer.
   TheModule = BEConsumer->takeModule();
 }
@@ -775,13 +779,12 @@ CodeGenAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
 
   // Load bitcode modules to link with, if we need to.
   if (LinkModules.empty())
-    for (auto &I : CI.getCodeGenOpts().LinkBitcodeFiles) {
-      const std::string &LinkBCFile = I.second;
-
-      auto BCBuf = CI.getFileManager().getBufferForFile(LinkBCFile);
+    for (const CodeGenOptions::BitcodeFileToLink &F :
+         CI.getCodeGenOpts().LinkBitcodeFiles) {
+      auto BCBuf = CI.getFileManager().getBufferForFile(F.Filename);
       if (!BCBuf) {
         CI.getDiagnostics().Report(diag::err_cannot_open_file)
-            << LinkBCFile << BCBuf.getError().message();
+            << F.Filename << BCBuf.getError().message();
         LinkModules.clear();
         return nullptr;
       }
@@ -791,12 +794,13 @@ CodeGenAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
       if (!ModuleOrErr) {
         handleAllErrors(ModuleOrErr.takeError(), [&](ErrorInfoBase &EIB) {
           CI.getDiagnostics().Report(diag::err_cannot_open_file)
-              << LinkBCFile << EIB.message();
+              << F.Filename << EIB.message();
         });
         LinkModules.clear();
         return nullptr;
       }
-      addLinkModule(ModuleOrErr.get().release(), I.first);
+      LinkModules.push_back(
+          {std::move(ModuleOrErr.get()), F.PropagateAttrs, F.LinkFlags});
     }
 
   CoverageSourceInfo *CoverageInfo = nullptr;
@@ -810,8 +814,8 @@ CodeGenAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
   std::unique_ptr<BackendConsumer> Result(new BackendConsumer(
       BA, CI.getDiagnostics(), CI.getHeaderSearchOpts(),
       CI.getPreprocessorOpts(), CI.getCodeGenOpts(), CI.getTargetOpts(),
-      CI.getLangOpts(), CI.getFrontendOpts().ShowTimers, InFile, LinkModules,
-      std::move(OS), *VMContext, CoverageInfo));
+      CI.getLangOpts(), CI.getFrontendOpts().ShowTimers, InFile,
+      std::move(LinkModules), std::move(OS), *VMContext, CoverageInfo));
   BEConsumer = Result.get();
   return std::move(Result);
 }