Fix PR4986. "r1024 = insert_subreg r1024, undef, 2" cannot be turned in an implicit_def. Instead, it's an identity copy so it should be eliminated. Also make sure to update livevariable kill information.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@82436 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 23 insertions, 10 deletions

diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index c690ac3..abab1ee 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -109,18 +109,15 @@ void LiveIntervals::releaseMemory() {
 }
 
 static bool CanTurnIntoImplicitDef(MachineInstr *MI, unsigned Reg,
-                                   const TargetInstrInfo *tii_) {
+                                   unsigned OpIdx, const TargetInstrInfo *tii_){
   unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
   if (tii_->isMoveInstr(*MI, SrcReg, DstReg, SrcSubReg, DstSubReg) &&
       Reg == SrcReg)
     return true;
 
-  if ((MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG ||
-       MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG) &&
-      MI->getOperand(2).getReg() == Reg)
+  if (OpIdx == 2 && MI->getOpcode() == TargetInstrInfo::SUBREG_TO_REG)
     return true;
-  if (MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG &&
-      MI->getOperand(1).getReg() == Reg)
+  if (OpIdx == 1 && MI->getOpcode() == TargetInstrInfo::EXTRACT_SUBREG)
     return true;
   return false;
 }
@@ -148,6 +145,20 @@ void LiveIntervals::processImplicitDefs() {
         continue;
       }
 
+      if (MI->getOpcode() == TargetInstrInfo::INSERT_SUBREG) {
+        MachineOperand &MO = MI->getOperand(2);
+        if (ImpDefRegs.count(MO.getReg())) {
+          // %reg1032<def> = INSERT_SUBREG %reg1032, undef, 2
+          // This is an identity copy, eliminate it now.
+          if (MO.isKill()) {
+            LiveVariables::VarInfo& vi = lv_->getVarInfo(MO.getReg());
+            vi.removeKill(MI);
+          }
+          MI->eraseFromParent();
+          continue;
+        }
+      }
+
       bool ChangedToImpDef = false;
       for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
         MachineOperand& MO = MI->getOperand(i);
@@ -159,13 +170,16 @@ void LiveIntervals::processImplicitDefs() {
         if (!ImpDefRegs.count(Reg))
           continue;
         // Use is a copy, just turn it into an implicit_def.
-        if (CanTurnIntoImplicitDef(MI, Reg, tii_)) {
+        if (CanTurnIntoImplicitDef(MI, Reg, i, tii_)) {
           bool isKill = MO.isKill();
           MI->setDesc(tii_->get(TargetInstrInfo::IMPLICIT_DEF));
           for (int j = MI->getNumOperands() - 1, ee = 0; j > ee; --j)
             MI->RemoveOperand(j);
-          if (isKill)
+          if (isKill) {
             ImpDefRegs.erase(Reg);
+            LiveVariables::VarInfo& vi = lv_->getVarInfo(Reg);
+            vi.removeKill(MI);
+          }
           ChangedToImpDef = true;
           break;
         }
@@ -738,8 +752,7 @@ void LiveIntervals::handleVirtualRegisterDef(MachineBasicBlock *mbb,
       MachineInstr *Kill = vi.Kills[i];
       MachineInstrIndex killIdx =
         getNextSlot(getUseIndex(getInstructionIndex(Kill)));
-      LiveRange LR(getMBBStartIdx(Kill->getParent()),
-                   killIdx, ValNo);
+      LiveRange LR(getMBBStartIdx(Kill->getParent()), killIdx, ValNo);
       interval.addRange(LR);
       ValNo->addKill(killIdx);
       DEBUG(errs() << " +" << LR);