Correctly handle replacement and removal of PHIs with one incoming register.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54374 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/CodeGen/UnreachableBlockElim.cpp b/lib/CodeGen/UnreachableBlockElim.cpp
index 19341ee721..ca682fd65a 100644
--- a/lib/CodeGen/UnreachableBlockElim.cpp
+++ b/lib/CodeGen/UnreachableBlockElim.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Pass.h"
 #include "llvm/Type.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Support/CFG.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Target/TargetInstrInfo.h"
@@ -128,10 +129,15 @@ bool UnreachableMachineBlockElim::runOnMachineFunction(MachineFunction &F) {
               start->RemoveOperand(i-1);
             }
           
-          if (start->getNumOperands() == 1) {
+          if (start->getNumOperands() == 3) {
             MachineInstr* phi = start;
+            unsigned Input = phi->getOperand(1).getReg();
+            unsigned Output = phi->getOperand(0).getReg();
+            
             start++;
             phi->eraseFromParent();
+            
+            F.getRegInfo().replaceRegWith(Output, Input);
           } else
             start++;
         }