Avoid iterating every operand of an instruction in StrongPHIElimination, since

we are only interested in the defs when discovering interferences.

This is a 28% speedup running StrongPHIElimination on 403.gcc.

llvm-svn: 122596

1 files changed, 3 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/StrongPHIElimination.cpp b/llvm/lib/CodeGen/StrongPHIElimination.cpp
index c1a76a6193a..f84fdbe5bc2 100644
--- a/llvm/lib/CodeGen/StrongPHIElimination.cpp
+++ b/llvm/lib/CodeGen/StrongPHIElimination.cpp
@@ -471,10 +471,9 @@ StrongPHIElimination::SplitInterferencesForBasicBlock(
     DenseMap<unsigned, unsigned>& ImmediateDominatingParent) {
   for (MachineBasicBlock::iterator BBI = MBB.begin(), BBE = MBB.end();
   BBI != BBE; ++BBI) {
-    for (unsigned i = 0, e = BBI->getNumOperands(); i != e; ++i) {
-      MachineOperand& MO = BBI->getOperand(i);
-      if (!MO.isReg() || !MO.isDef())
-        continue;
+    for (MachineInstr::const_mop_iterator I = BBI->operands_begin(),
+         E = BBI->operands_end(); I != E && I->isReg() && I->isDef(); ++I) {
+      const MachineOperand& MO = *I;
 
       unsigned DestReg = MO.getReg();
       if (!DestReg || !TargetRegisterInfo::isVirtualRegister(DestReg))