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author | Bob Wilson <bob.wilson@apple.com> | 2009-10-27 23:49:38 +0000 |
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committer | Bob Wilson <bob.wilson@apple.com> | 2009-10-27 23:49:38 +0000 |
commit | cd4f04d6bcb7aefa24d92582fbadfe17519f4756 (patch) | |
tree | 154762d67c0c4a8d677aeef3bd023b5a1f0f719a /lib/CodeGen | |
parent | 03236140fa4ef316a605717e090276d6a0d42828 (diff) | |
download | external_llvm-cd4f04d6bcb7aefa24d92582fbadfe17519f4756.zip external_llvm-cd4f04d6bcb7aefa24d92582fbadfe17519f4756.tar.gz external_llvm-cd4f04d6bcb7aefa24d92582fbadfe17519f4756.tar.bz2 |
Record CodeGen optimization level in the BranchFolding pass so that we can
use it to control tail merging when there is a tradeoff between performance
and code size. When there is only 1 instruction in the common tail, we have
been merging. That can be good for code size but is a definite loss for
performance. Now we will avoid tail merging in that case when the
optimization level is "Aggressive", i.e., "-O3". Radar 7338114.
Since the IfConversion pass invokes BranchFolding, it too needs to know
the optimization level. Note that I removed the RegisterPass instantiation
for IfConversion because it required a default constructor. If someone
wants to keep that for some reason, we can add a default constructor with
a hard-wired optimization level.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85346 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen')
-rw-r--r-- | lib/CodeGen/BranchFolding.cpp | 14 | ||||
-rw-r--r-- | lib/CodeGen/BranchFolding.h | 10 | ||||
-rw-r--r-- | lib/CodeGen/IfConversion.cpp | 13 | ||||
-rw-r--r-- | lib/CodeGen/LLVMTargetMachine.cpp | 2 |
4 files changed, 24 insertions, 15 deletions
diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp index 66c5aa5..11777d5 100644 --- a/lib/CodeGen/BranchFolding.cpp +++ b/lib/CodeGen/BranchFolding.cpp @@ -50,8 +50,9 @@ TailMergeThreshold("tail-merge-threshold", char BranchFolderPass::ID = 0; -FunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) { - return new BranchFolderPass(DefaultEnableTailMerge); +FunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge, + CodeGenOpt::Level OptLevel) { + return new BranchFolderPass(DefaultEnableTailMerge, OptLevel); } bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) { @@ -63,7 +64,8 @@ bool BranchFolderPass::runOnMachineFunction(MachineFunction &MF) { -BranchFolder::BranchFolder(bool defaultEnableTailMerge) { +BranchFolder::BranchFolder(bool defaultEnableTailMerge, CodeGenOpt::Level OL) { + OptLevel = OL; switch (FlagEnableTailMerge) { case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break; case cl::BOU_TRUE: EnableTailMerge = true; break; @@ -470,7 +472,8 @@ unsigned BranchFolder::ComputeSameTails(unsigned CurHash, I->second, TrialBBI1, TrialBBI2); // If we will have to split a block, there should be at least - // minCommonTailLength instructions in common; if not, at worst + // minCommonTailLength instructions in common; if not, and if we are not + // optimizing for performance at the expense of code size, at worst // we will be replacing a fallthrough into the common tail with a // branch, which at worst breaks even with falling through into // the duplicated common tail, so 1 instruction in common is enough. @@ -478,7 +481,8 @@ unsigned BranchFolder::ComputeSameTails(unsigned CurHash, // tail if there is one. // (Empty blocks will get forwarded and need not be considered.) if (CommonTailLen >= minCommonTailLength || - (CommonTailLen > 0 && + (OptLevel != CodeGenOpt::Aggressive && + CommonTailLen > 0 && (TrialBBI1==CurMPIter->second->begin() || TrialBBI2==I->second->begin()))) { if (CommonTailLen > maxCommonTailLength) { diff --git a/lib/CodeGen/BranchFolding.h b/lib/CodeGen/BranchFolding.h index 9763e33..5d35525 100644 --- a/lib/CodeGen/BranchFolding.h +++ b/lib/CodeGen/BranchFolding.h @@ -12,6 +12,7 @@ #include "llvm/CodeGen/MachineBasicBlock.h" #include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/Target/TargetMachine.h" #include <vector> namespace llvm { @@ -23,7 +24,7 @@ namespace llvm { class BranchFolder { public: - explicit BranchFolder(bool defaultEnableTailMerge); + explicit BranchFolder(bool defaultEnableTailMerge, CodeGenOpt::Level OL); bool OptimizeFunction(MachineFunction &MF, const TargetInstrInfo *tii, @@ -37,6 +38,7 @@ namespace llvm { typedef std::pair<MPIterator, MachineBasicBlock::iterator> SameTailElt; std::vector<SameTailElt> SameTails; + CodeGenOpt::Level OptLevel; bool EnableTailMerge; const TargetInstrInfo *TII; const TargetRegisterInfo *TRI; @@ -73,8 +75,10 @@ namespace llvm { public BranchFolder { public: static char ID; - explicit BranchFolderPass(bool defaultEnableTailMerge) - : MachineFunctionPass(&ID), BranchFolder(defaultEnableTailMerge) {} + explicit BranchFolderPass(bool defaultEnableTailMerge, + CodeGenOpt::Level OptLevel) + : MachineFunctionPass(&ID), + BranchFolder(defaultEnableTailMerge, OptLevel) {} virtual bool runOnMachineFunction(MachineFunction &MF); virtual const char *getPassName() const { return "Control Flow Optimizer"; } diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp index 45f08b1..be9e1f1 100644 --- a/lib/CodeGen/IfConversion.cpp +++ b/lib/CodeGen/IfConversion.cpp @@ -148,9 +148,11 @@ namespace { const TargetInstrInfo *TII; bool MadeChange; int FnNum; + CodeGenOpt::Level OptLevel; public: static char ID; - IfConverter() : MachineFunctionPass(&ID), FnNum(-1) {} + IfConverter(CodeGenOpt::Level OL) : + MachineFunctionPass(&ID), FnNum(-1), OptLevel(OL) {} virtual bool runOnMachineFunction(MachineFunction &MF); virtual const char *getPassName() const { return "If Converter"; } @@ -219,10 +221,9 @@ namespace { char IfConverter::ID = 0; } -static RegisterPass<IfConverter> -X("if-converter", "If Converter"); - -FunctionPass *llvm::createIfConverterPass() { return new IfConverter(); } +FunctionPass *llvm::createIfConverterPass(CodeGenOpt::Level OptLevel) { + return new IfConverter(OptLevel); +} bool IfConverter::runOnMachineFunction(MachineFunction &MF) { TLI = MF.getTarget().getTargetLowering(); @@ -362,7 +363,7 @@ bool IfConverter::runOnMachineFunction(MachineFunction &MF) { BBAnalysis.clear(); if (MadeChange) { - BranchFolder BF(false); + BranchFolder BF(false, OptLevel); BF.OptimizeFunction(MF, TII, MF.getTarget().getRegisterInfo(), getAnalysisIfAvailable<MachineModuleInfo>()); diff --git a/lib/CodeGen/LLVMTargetMachine.cpp b/lib/CodeGen/LLVMTargetMachine.cpp index e58a9ca..1a2daef 100644 --- a/lib/CodeGen/LLVMTargetMachine.cpp +++ b/lib/CodeGen/LLVMTargetMachine.cpp @@ -329,7 +329,7 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM, // Branch folding must be run after regalloc and prolog/epilog insertion. if (OptLevel != CodeGenOpt::None) { - PM.add(createBranchFoldingPass(getEnableTailMergeDefault())); + PM.add(createBranchFoldingPass(getEnableTailMergeDefault(), OptLevel)); printAndVerify(PM); } |