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.

llvm-svn: 122608

1 files changed, 8 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/StrongPHIElimination.cpp b/llvm/lib/CodeGen/StrongPHIElimination.cpp
index f84fdbe5bc2..5713e6aed29 100644
--- a/llvm/lib/CodeGen/StrongPHIElimination.cpp
+++ b/llvm/lib/CodeGen/StrongPHIElimination.cpp
@@ -472,9 +472,16 @@ StrongPHIElimination::SplitInterferencesForBasicBlock(
   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;