Now that instruction optzns can update the iterator as they go, we can

have objectsize folding recursively simplify away their result when it
folds.  It is important to catch this here, because otherwise we won't
eliminate the cross-block values at isel and other times.

llvm-svn: 123524

1 files changed, 16 insertions, 10 deletions

diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
index ae827871b54..921cec83512 100644
--- a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -42,6 +42,7 @@
 #include "llvm/Support/PatternMatch.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Support/IRBuilder.h"
+#include "llvm/Support/ValueHandle.h"
 using namespace llvm;
 using namespace llvm::PatternMatch;
 
@@ -634,8 +635,18 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
     bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1);
     const Type *ReturnTy = CI->getType();
     Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL);    
-    CI->replaceAllUsesWith(RetVal);
-    CI->eraseFromParent();
+    
+    // Substituting this can cause recursive simplifications, which can
+    // invalidate our iterator.  Use a WeakVH to hold onto it in case this
+    // happens.
+    WeakVH IterHandle(CurInstIterator);
+    
+    ReplaceAndSimplifyAllUses(CI, RetVal, TLI ? TLI->getTargetData() : 0, DT);
+
+    // If the iterator instruction was recursively deleted, start over at the
+    // start of the block.
+    if (IterHandle != CurInstIterator)
+      CurInstIterator = BB->begin();
     return true;
   }
 
@@ -653,6 +664,7 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
   CodeGenPrepareFortifiedLibCalls Simplifier;
   return Simplifier.fold(CI, TD);
 }
+
 //===----------------------------------------------------------------------===//
 // Memory Optimization
 //===----------------------------------------------------------------------===//
@@ -1076,14 +1088,8 @@ bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
   SunkAddrs.clear();
 
   CurInstIterator = BB.begin();
-  for (BasicBlock::iterator E = BB.end(); CurInstIterator != E; ) {
-    Instruction *I = CurInstIterator++;
-
-    if (CallInst *CI = dyn_cast<CallInst>(I))
-      MadeChange |= OptimizeCallInst(CI);
-    else
-      MadeChange |= OptimizeInst(I);
-  }
+  for (BasicBlock::iterator E = BB.end(); CurInstIterator != E; )
+    MadeChange |= OptimizeInst(CurInstIterator++);
 
   return MadeChange;
 }