Auto merge of #48346 - emilio:pgo, r=alexcrichton

Add basic PGO support.

This PR adds two mutually exclusive options for profile usage and generation using LLVM's instruction profile generation (the same as clang uses), `-C pgo-use` and `-C pgo-gen`.

See each commit for details.

src/rustllvm/PassWrapper.cpp

@@ -44,6 +44,10 @@
 
 #include "llvm-c/Transforms/PassManagerBuilder.h"
 
+#if LLVM_VERSION_GE(4, 0)
+#define PGO_AVAILABLE
+#endif
+
 using namespace llvm;
 using namespace llvm::legacy;
 
@@ -428,12 +432,27 @@ extern "C" void LLVMRustAddAnalysisPasses(LLVMTargetMachineRef TM,
 
 extern "C" void LLVMRustConfigurePassManagerBuilder(
     LLVMPassManagerBuilderRef PMBR, LLVMRustCodeGenOptLevel OptLevel,
-    bool MergeFunctions, bool SLPVectorize, bool LoopVectorize) {
+    bool MergeFunctions, bool SLPVectorize, bool LoopVectorize,
+    const char* PGOGenPath, const char* PGOUsePath) {
   // Ignore mergefunc for now as enabling it causes crashes.
   // unwrap(PMBR)->MergeFunctions = MergeFunctions;
   unwrap(PMBR)->SLPVectorize = SLPVectorize;
   unwrap(PMBR)->OptLevel = fromRust(OptLevel);
   unwrap(PMBR)->LoopVectorize = LoopVectorize;
+
+#ifdef PGO_AVAILABLE
+  if (PGOGenPath) {
+    assert(!PGOUsePath);
+    unwrap(PMBR)->EnablePGOInstrGen = true;
+    unwrap(PMBR)->PGOInstrGen = PGOGenPath;
+  }
+  if (PGOUsePath) {
+    assert(!PGOGenPath);
+    unwrap(PMBR)->PGOInstrUse = PGOUsePath;
+  }
+#else
+  assert(!PGOGenPath && !PGOUsePath && "Should've caught earlier");
+#endif
 }
 
 // Unfortunately, the LLVM C API doesn't provide a way to set the `LibraryInfo`
@@ -766,6 +785,15 @@ LLVMRustThinLTOAvailable() {
 #endif
 }
 
+extern "C" bool
+LLVMRustPGOAvailable() {
+#ifdef PGO_AVAILABLE
+  return true;
+#else
+  return false;
+#endif
+}
+
 #if LLVM_VERSION_GE(4, 0)
 
 // Here you'll find an implementation of ThinLTO as used by the Rust compiler

src/rustllvm/RustWrapper.cpp

@@ -1021,6 +1021,7 @@ enum class LLVMRustDiagnosticKind {
   OptimizationRemarkAnalysisAliasing,
   OptimizationRemarkOther,
   OptimizationFailure,
+  PGOProfile,
 };
 
 static LLVMRustDiagnosticKind toRust(DiagnosticKind Kind) {
@@ -1043,6 +1044,8 @@ static LLVMRustDiagnosticKind toRust(DiagnosticKind Kind) {
     return LLVMRustDiagnosticKind::OptimizationRemarkAnalysisFPCommute;
   case DK_OptimizationRemarkAnalysisAliasing:
     return LLVMRustDiagnosticKind::OptimizationRemarkAnalysisAliasing;
+  case DK_PGOProfile:
+    return LLVMRustDiagnosticKind::PGOProfile;
   default:
     return (Kind >= DK_FirstRemark && Kind <= DK_LastRemark)
                ? LLVMRustDiagnosticKind::OptimizationRemarkOther