Don't assume that only Uses can be kills. Defs are marked as kills initially

when there are no uses. This fixes a dangling-pointer bug, where pointers to
deleted instructions were not removed from kills lists. More info here:
http://lists.cs.uiuc.edu/pipermail/llvmdev/2007-July/009749.html

llvm-svn: 40131

2 files changed, 8 insertions, 10 deletions

diff --git a/llvm/lib/CodeGen/LiveVariables.cpp b/llvm/lib/CodeGen/LiveVariables.cpp
index 504b607b857..d1ebaf102fc 100644
--- a/llvm/lib/CodeGen/LiveVariables.cpp
+++ b/llvm/lib/CodeGen/LiveVariables.cpp
@@ -582,15 +582,13 @@ void LiveVariables::instructionChanged(MachineInstr *OldMI,
         if (VI.DefInst == OldMI)
           VI.DefInst = NewMI;
       }
-      if (MO.isUse()) {
-        if (MO.isKill()) {
-          MO.unsetIsKill();
-          addVirtualRegisterKilled(Reg, NewMI);
-        }
-        // If this is a kill of the value, update the VI kills list.
-        if (VI.removeKill(OldMI))
-          VI.Kills.push_back(NewMI);   // Yes, there was a kill of it
+      if (MO.isKill()) {
+        MO.unsetIsKill();
+        addVirtualRegisterKilled(Reg, NewMI);
       }
+      // If this is a kill of the value, update the VI kills list.
+      if (VI.removeKill(OldMI))
+        VI.Kills.push_back(NewMI);   // Yes, there was a kill of it
     }
   }
 }
diff --git a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
index b714bac86a1..4619fd7f4f0 100644
--- a/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/llvm/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -955,7 +955,7 @@ MachineOperand *SimpleRegisterCoalescing::findDefOperand(MachineInstr *MI, unsig
 void SimpleRegisterCoalescing::unsetRegisterKill(MachineInstr *MI, unsigned Reg) {
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     MachineOperand &MO = MI->getOperand(i);
-    if (MO.isReg() && MO.isUse() && MO.isKill() && MO.getReg() &&
+    if (MO.isReg() && MO.isKill() && MO.getReg() &&
         mri_->regsOverlap(rep(MO.getReg()), Reg))
       MO.unsetIsKill();
   }
@@ -979,7 +979,7 @@ void SimpleRegisterCoalescing::unsetRegisterKills(unsigned Start, unsigned End,
 
     for (unsigned i = 0, NumOps = MI->getNumOperands(); i != NumOps; ++i) {
       MachineOperand &MO = MI->getOperand(i);
-      if (MO.isReg() && MO.isUse() && MO.isKill() && MO.getReg() &&
+      if (MO.isReg() && MO.isKill() && MO.getReg() &&
           mri_->regsOverlap(rep(MO.getReg()), Reg)) {
         MO.unsetIsKill();
       }