From 7bb413e3baf859e69b9c844108a0bd71eb176140 Mon Sep 17 00:00:00 2001 From: Chad Rosier Date: Fri, 31 Oct 2014 19:02:38 +0000 Subject: [PATCH] [AArch64] Check Dest Register Liveness in CondOpt pass. Our internal test reveals such case should not be transformed: cmp x17, #3 b.lt .LBB10_15 ... subs x12, x12, #1 b.gt .LBB10_1 where x12 is a liveout, becomes: cmp x17, #2 b.le .LBB10_15 ... subs x12, x12, #2 b.ge .LBB10_1 Unable to provide test case as it's difficult to reproduce on community branch. http://reviews.llvm.org/D6048 Patch by Zhaoshi Zheng ! llvm-svn: 220987 --- llvm/lib/Target/AArch64/AArch64ConditionOptimizer.cpp | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/llvm/lib/Target/AArch64/AArch64ConditionOptimizer.cpp b/llvm/lib/Target/AArch64/AArch64ConditionOptimizer.cpp index b04e047..0fbd3c6 100644 --- a/llvm/lib/Target/AArch64/AArch64ConditionOptimizer.cpp +++ b/llvm/lib/Target/AArch64/AArch64ConditionOptimizer.cpp @@ -62,6 +62,7 @@ #include "llvm/ADT/DepthFirstIterator.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/Statistic.h" +#include "llvm/CodeGen/LiveIntervalAnalysis.h" #include "llvm/CodeGen/MachineDominators.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineFunctionPass.h" @@ -115,6 +116,7 @@ void initializeAArch64ConditionOptimizerPass(PassRegistry &); INITIALIZE_PASS_BEGIN(AArch64ConditionOptimizer, "aarch64-condopt", "AArch64 CondOpt Pass", false, false) INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree) +INITIALIZE_PASS_DEPENDENCY(LiveIntervals) INITIALIZE_PASS_END(AArch64ConditionOptimizer, "aarch64-condopt", "AArch64 CondOpt Pass", false, false) @@ -125,6 +127,8 @@ FunctionPass *llvm::createAArch64ConditionOptimizerPass() { void AArch64ConditionOptimizer::getAnalysisUsage(AnalysisUsage &AU) const { AU.addRequired(); AU.addPreserved(); + AU.addRequired(); + AU.addPreserved(); MachineFunctionPass::getAnalysisUsage(AU); } @@ -134,13 +138,11 @@ void AArch64ConditionOptimizer::getAnalysisUsage(AnalysisUsage &AU) const { MachineInstr *AArch64ConditionOptimizer::findSuitableCompare( MachineBasicBlock *MBB) { MachineBasicBlock::iterator I = MBB->getFirstTerminator(); - if (I == MBB->end()) { + if (I == MBB->end()) return nullptr; - } - if (I->getOpcode() != AArch64::Bcc) { - return nullptr; - } + if (I->getOpcode() != AArch64::Bcc) + return nullptr; // Now find the instruction controlling the terminator. for (MachineBasicBlock::iterator B = MBB->begin(); I != B;) { @@ -153,7 +155,11 @@ MachineInstr *AArch64ConditionOptimizer::findSuitableCompare( // cmn is an alias for adds with a dead destination register. case AArch64::ADDSWri: case AArch64::ADDSXri: - return I; + if (I->getOperand(0).isDead()) + return I; + + DEBUG(dbgs() << "Destination of cmp is not dead, " << *I << '\n'); + return nullptr; // Prevent false positive case like: // cmp w19, #0 -- 2.7.4