Use getVRegDef() instead of def_iterator. This leads to fewer defs being added

with 2-address instructions, for about a 3.5% speedup of StrongPHIElimination on
403.gcc.

llvm-svn: 122635

llvm/lib/CodeGen/StrongPHIElimination.cpp

@@ -233,10 +233,9 @@ bool StrongPHIElimination::runOnMachineFunction(MachineFunction& MF) {
         addReg(SrcReg);
         unionRegs(DestReg, SrcReg);
 
-        for (MachineRegisterInfo::def_iterator DI = MRI->def_begin(SrcReg),
-             DE = MRI->def_end(); DI != DE; ++DI) {
-          PHISrcDefs[DI->getParent()].push_back(&*DI);
-        }
+        MachineInstr* DefMI = MRI->getVRegDef(SrcReg);
+        if (DefMI)
+          PHISrcDefs[DefMI->getParent()].push_back(DefMI);
       }
     }
   }