Revert the optimization in r122596. It is correct for all current targets, but
it relies on assumptions that may not be true in the future.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122608 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/StrongPHIElimination.cpp b/lib/CodeGen/StrongPHIElimination.cpp
index f84fdbe..5713e6a 100644
--- a/lib/CodeGen/StrongPHIElimination.cpp
+++ b/lib/CodeGen/StrongPHIElimination.cpp
@@ -472,9 +472,16 @@
for (MachineBasicBlock::iterator BBI = MBB.begin(), BBE = MBB.end();
BBI != BBE; ++BBI) {
for (MachineInstr::const_mop_iterator I = BBI->operands_begin(),
- E = BBI->operands_end(); I != E && I->isReg() && I->isDef(); ++I) {
+ E = BBI->operands_end(); I != E; ++I) {
const MachineOperand& MO = *I;
+ // FIXME: This would be faster if it were possible to bail out of checking
+ // an instruction's operands after the explicit defs, but this is incorrect
+ // for variadic instructions, which may appear before register allocation
+ // in the future.
+ if (!MO.isReg() || !MO.isDef())
+ continue;
+
unsigned DestReg = MO.getReg();
if (!DestReg || !TargetRegisterInfo::isVirtualRegister(DestReg))
continue;