[llvm] r235532 - [AArch64] Use MachineRegisterInfo instead of LiveIntervals to calculate liveness. NFC.

[Pete Cooper]

Author: pete
Date: Wed Apr 22 13:05:13 2015
New Revision: 235532

URL: http://llvm.org/viewvc/llvm-project?rev=235532&view=rev
Log:
[AArch64] Use MachineRegisterInfo instead of LiveIntervals to calculate liveness.  NFC.

The CondOpt pass currently uses LiveIntervals to set the dead flag on a def.  This patch uses MachineRegisterInfo::use_empty instead as that is equivalent to the def being dead.

This removes an instance of LiveIntervals in the pass manager pipeline and saves 3.8% of compile time on llc conpiled for AArch64.

Reviewed by Chad Rosier and Zhaoshi.

Modified:
    llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp

Modified: llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp?rev=235532&r1=235531&r2=235532&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/AArch64ConditionOptimizer.cpp Wed Apr 22 13:05:13 2015
@@ -67,6 +67,7 @@
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
@@ -86,6 +87,7 @@ namespace {
 class AArch64ConditionOptimizer : public MachineFunctionPass {
   const TargetInstrInfo *TII;
   MachineDominatorTree *DomTree;
+  const MachineRegisterInfo *MRI;
 
 public:
   // Stores immediate, compare instruction opcode and branch condition (in this
@@ -116,7 +118,6 @@ void initializeAArch64ConditionOptimizer
 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)
 
@@ -127,8 +128,6 @@ FunctionPass *llvm::createAArch64Conditi
 void AArch64ConditionOptimizer::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.addRequired<MachineDominatorTree>();
   AU.addPreserved<MachineDominatorTree>();
-  AU.addRequired<LiveIntervals>();
-  AU.addPreserved<LiveIntervals>();
   MachineFunctionPass::getAnalysisUsage(AU);
 }
 
@@ -155,7 +154,7 @@ MachineInstr *AArch64ConditionOptimizer:
     // cmn is an alias for adds with a dead destination register.
     case AArch64::ADDSWri:
     case AArch64::ADDSXri:
-      if (I->getOperand(0).isDead())
+      if (MRI->use_empty(I->getOperand(0).getReg()))
         return I;
 
       DEBUG(dbgs() << "Destination of cmp is not dead, " << *I << '\n');
@@ -306,6 +305,7 @@ bool AArch64ConditionOptimizer::runOnMac
                << "********** Function: " << MF.getName() << '\n');
   TII = MF.getSubtarget().getInstrInfo();
   DomTree = &getAnalysis<MachineDominatorTree>();
+  MRI = &MF.getRegInfo();
 
   bool Changed = false;