[PGO] Promote indirect calls to conditional direct calls with value-p…

…rofile

This patch implements the transformation that promotes indirect calls to
conditional direct calls when the indirect-call value profile meta-data is
available.

Differential Revision: http://reviews.llvm.org/D17864

llvm-svn: 267815

llvm/include/llvm/InitializePasses.h

@@ -124,6 +124,7 @@ void initializeAAResultsWrapperPassPass(PassRegistry &);
 void initializeGCOVProfilerPass(PassRegistry&);
 void initializePGOInstrumentationGenPass(PassRegistry&);
 void initializePGOInstrumentationUsePass(PassRegistry&);
+void initializePGOIndirectCallPromotionPass(PassRegistry&);
 void initializeInstrProfilingLegacyPassPass(PassRegistry &);
 void initializeAddressSanitizerPass(PassRegistry&);
 void initializeAddressSanitizerModulePass(PassRegistry&);

llvm/include/llvm/LinkAllPasses.h

@@ -91,6 +91,7 @@ namespace {
       (void) llvm::createGCOVProfilerPass();
       (void) llvm::createPGOInstrumentationGenPass();
       (void) llvm::createPGOInstrumentationUsePass();
+      (void) llvm::createPGOIndirectCallPromotionPass();
       (void) llvm::createInstrProfilingLegacyPass();
       (void) llvm::createFunctionImportPass();
       (void) llvm::createFunctionInliningPass();

llvm/include/llvm/Transforms/Instrumentation.h

@@ -83,6 +83,7 @@ ModulePass *createGCOVProfilerPass(const GCOVOptions &Options =
 ModulePass *createPGOInstrumentationGenPass();
 ModulePass *
 createPGOInstrumentationUsePass(StringRef Filename = StringRef(""));
+ModulePass *createPGOIndirectCallPromotionPass(bool InLTO = false);
 
 /// Options for the frontend instrumentation based profiling pass.
 struct InstrProfOptions {

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -371,10 +371,13 @@ void PassManagerBuilder::populateModulePassManager(
     MPM.add(createCFGSimplificationPass()); // Clean up after IPCP & DAE
   }
 
-  if (!PerformThinLTO)
+  if (!PerformThinLTO) {
     /// PGO instrumentation is added during the compile phase for ThinLTO, do
     /// not run it a second time
     addPGOInstrPasses(MPM);
+    // Indirect call promotion that promotes intra-module targets only.
+    MPM.add(createPGOIndirectCallPromotionPass());
+  }
 
   if (EnableNonLTOGlobalsModRef)
     // We add a module alias analysis pass here. In part due to bugs in the
@@ -585,6 +588,12 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
   // Infer attributes about declarations if possible.
   PM.add(createInferFunctionAttrsLegacyPass());
 
+  // Indirect call promotion. This should promote all the targets that are left
+  // by the earlier promotion pass that promotes intra-module targets.
+  // This two-step promotion is to save the compile time. For LTO, it should
+  // produce the same result as if we only do promotion here.
+  PM.add(createPGOIndirectCallPromotionPass(true));
+
   // Propagate constants at call sites into the functions they call.  This
   // opens opportunities for globalopt (and inlining) by substituting function
   // pointers passed as arguments to direct uses of functions.

llvm/lib/Transforms/Instrumentation/CMakeLists.txt

@@ -4,6 +4,7 @@ add_llvm_library(LLVMInstrumentation
   DataFlowSanitizer.cpp
   GCOVProfiling.cpp
   MemorySanitizer.cpp
+  IndirectCallPromotion.cpp
   Instrumentation.cpp
   InstrProfiling.cpp
   PGOInstrumentation.cpp