Use phi ranges to simplify code. No functionality change intended.

llvm-svn: 321585
diff --git a/llvm/lib/CodeGen/WinEHPrepare.cpp b/llvm/lib/CodeGen/WinEHPrepare.cpp
index 7ad8473..0b16a11 100644
--- a/llvm/lib/CodeGen/WinEHPrepare.cpp
+++ b/llvm/lib/CodeGen/WinEHPrepare.cpp
@@ -838,17 +838,11 @@
     for (auto &BBMapping : Orig2Clone) {
       BasicBlock *OldBlock = BBMapping.first;
       BasicBlock *NewBlock = BBMapping.second;
-      for (Instruction &OldI : *OldBlock) {
-        auto *OldPN = dyn_cast<PHINode>(&OldI);
-        if (!OldPN)
-          break;
-        UpdatePHIOnClonedBlock(OldPN, /*IsForOldBlock=*/true);
+      for (PHINode &OldPN : OldBlock->phis()) {
+        UpdatePHIOnClonedBlock(&OldPN, /*IsForOldBlock=*/true);
       }
-      for (Instruction &NewI : *NewBlock) {
-        auto *NewPN = dyn_cast<PHINode>(&NewI);
-        if (!NewPN)
-          break;
-        UpdatePHIOnClonedBlock(NewPN, /*IsForOldBlock=*/false);
+      for (PHINode &NewPN : NewBlock->phis()) {
+        UpdatePHIOnClonedBlock(&NewPN, /*IsForOldBlock=*/false);
       }
     }
 
@@ -858,17 +852,13 @@
       BasicBlock *OldBlock = BBMapping.first;
       BasicBlock *NewBlock = BBMapping.second;
       for (BasicBlock *SuccBB : successors(NewBlock)) {
-        for (Instruction &SuccI : *SuccBB) {
-          auto *SuccPN = dyn_cast<PHINode>(&SuccI);
-          if (!SuccPN)
-            break;
-
+        for (PHINode &SuccPN : SuccBB->phis()) {
           // Ok, we have a PHI node.  Figure out what the incoming value was for
           // the OldBlock.
-          int OldBlockIdx = SuccPN->getBasicBlockIndex(OldBlock);
+          int OldBlockIdx = SuccPN.getBasicBlockIndex(OldBlock);
           if (OldBlockIdx == -1)
             break;
-          Value *IV = SuccPN->getIncomingValue(OldBlockIdx);
+          Value *IV = SuccPN.getIncomingValue(OldBlockIdx);
 
           // Remap the value if necessary.
           if (auto *Inst = dyn_cast<Instruction>(IV)) {
@@ -877,7 +867,7 @@
               IV = I->second;
           }
 
-          SuccPN->addIncoming(IV, NewBlock);
+          SuccPN.addIncoming(IV, NewBlock);
         }
       }
     }