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Move whole-program virtual call optimization pass after function attribute inference in LTO pipeline. 

As a result of D18634 we no longer infer certain attributes on linkonce_odr
functions at compile time, and may only infer them at LTO time. The readnone
attribute in particular is required for virtual constant propagation (part
of whole-program virtual call optimization) to work correctly.

This change moves the whole-program virtual call optimization pass after
the function attribute inference passes, and enables the attribute inference
passes at opt level 1, so that virtual constant propagation has a chance to
work correctly for linkonce_odr functions.

Differential Revision: http://reviews.llvm.org/D20643

llvm-svn: 270765
This commit is contained in:
Peter Collingbourne 2016-05-25 21:26:14 +00:00
parent fa814259ad
commit fad596aa81
2 changed files with 26 additions and 24 deletions
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1
llvm/include/llvm/Transforms/IPO/PassManagerBuilder.h
View File

@ -161,7 +161,6 @@ private:
legacy::PassManagerBase &PM) const;
void addInitialAliasAnalysisPasses(legacy::PassManagerBase &PM) const;
void addLTOOptimizationPasses(legacy::PassManagerBase &PM);
void addEarlyLTOOptimizationPasses(legacy::PassManagerBase &PM);
void addLateLTOOptimizationPasses(legacy::PassManagerBase &PM);
void addPGOInstrPasses(legacy::PassManagerBase &MPM);
void addFunctionSimplificationPasses(legacy::PassManagerBase &MPM);

49
llvm/lib/Transforms/IPO/PassManagerBuilder.cpp
View File

@ -567,6 +567,10 @@ void PassManagerBuilder::populateModulePassManager(
}
void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
// Remove unused virtual tables to improve the quality of code generated by
// whole-program devirtualization and bitset lowering.
PM.add(createGlobalDCEPass());
// Provide AliasAnalysis services for optimizations.
addInitialAliasAnalysisPasses(PM);
@ -579,20 +583,32 @@ 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(createPGOIndirectCallPromotionLegacyPass(true));
if (OptLevel > 1) {
// 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(createPGOIndirectCallPromotionLegacyPass(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.
PM.add(createIPSCCPPass());
// 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.
PM.add(createIPSCCPPass());
}
// Now that we internalized some globals, see if we can hack on them!
// Infer attributes about definitions. The readnone attribute in particular is
// required for virtual constant propagation.
PM.add(createPostOrderFunctionAttrsLegacyPass());
PM.add(createReversePostOrderFunctionAttrsPass());
// Apply whole-program devirtualization and virtual constant propagation.
PM.add(createWholeProgramDevirtPass());
// That's all we need at opt level 1.
if (OptLevel == 1)
return;
// Now that we internalized some globals, see if we can hack on them!
PM.add(createGlobalOptimizerPass());
// Promote any localized global vars.
PM.add(createPromoteMemoryToRegisterPass());
@ -694,16 +710,6 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
PM.add(createJumpThreadingPass());
}
void PassManagerBuilder::addEarlyLTOOptimizationPasses(
legacy::PassManagerBase &PM) {
// Remove unused virtual tables to improve the quality of code generated by
// whole-program devirtualization and bitset lowering.
PM.add(createGlobalDCEPass());
// Apply whole-program devirtualization and virtual constant propagation.
PM.add(createWholeProgramDevirtPass());
}
void PassManagerBuilder::addLateLTOOptimizationPasses(
legacy::PassManagerBase &PM) {
// Delete basic blocks, which optimization passes may have killed.
@ -746,9 +752,6 @@ void PassManagerBuilder::populateLTOPassManager(legacy::PassManagerBase &PM) {
PM.add(createVerifierPass());
if (OptLevel != 0)
addEarlyLTOOptimizationPasses(PM);
if (OptLevel > 1)
addLTOOptimizationPasses(PM);
// Create a function that performs CFI checks for cross-DSO calls with targets