Merge 81175 from mainline.

Fix PR4882, by making MemCpyOpt not dereference removed stores to get the
context for the newly created operations.

llvm-svn: 81693

Author: tlattner

llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp

@@ -338,13 +338,15 @@ static RegisterPass<MemCpyOpt> X("memcpyopt",
 bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator& BBI) {
   if (SI->isVolatile()) return false;
 
+  LLVMContext &Context = SI->getContext();
+
   // There are two cases that are interesting for this code to handle: memcpy
   // and memset.  Right now we only handle memset.
 
   // Ensure that the value being stored is something that can be memset'able a
   // byte at a time like "0" or "-1" or any width, as well as things like
   // 0xA0A0A0A0 and 0.0.
-  Value *ByteVal = isBytewiseValue(SI->getOperand(0), SI->getContext());
+  Value *ByteVal = isBytewiseValue(SI->getOperand(0), Context);
   if (!ByteVal)
     return false;
 
@@ -385,8 +387,7 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator& BBI) {
     if (NextStore->isVolatile()) break;
 
     // Check to see if this stored value is of the same byte-splattable value.
-    if (ByteVal != isBytewiseValue(NextStore->getOperand(0), 
-                                   NextStore->getContext()))
+    if (ByteVal != isBytewiseValue(NextStore->getOperand(0), Context))
       break;
 
     // Check to see if this store is to a constant offset from the start ptr.
@@ -406,7 +407,6 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator& BBI) {
   // store as well.  We try to avoid this unless there is at least something
   // interesting as a small compile-time optimization.
   Ranges.addStore(0, SI);
-
 
   Function *MemSetF = 0;
 
@@ -430,28 +430,25 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator& BBI) {
     BasicBlock::iterator InsertPt = BI;
 
     if (MemSetF == 0) {
-      const Type *Tys[] = {Type::getInt64Ty(SI->getContext())};
-      MemSetF = Intrinsic::getDeclaration(M, Intrinsic::memset,
-                                          Tys, 1);
-   }
+      const Type *Ty = Type::getInt64Ty(Context);
+      MemSetF = Intrinsic::getDeclaration(M, Intrinsic::memset, &Ty, 1);
+    }
 
     // Get the starting pointer of the block.
     StartPtr = Range.StartPtr;
 
     // Cast the start ptr to be i8* as memset requires.
-    const Type *i8Ptr =
-          PointerType::getUnqual(Type::getInt8Ty(SI->getContext()));
+    const Type *i8Ptr = PointerType::getUnqual(Type::getInt8Ty(Context));
     if (StartPtr->getType() != i8Ptr)
       StartPtr = new BitCastInst(StartPtr, i8Ptr, StartPtr->getName(),
                                  InsertPt);
 
     Value *Ops[] = {
       StartPtr, ByteVal,   // Start, value
       // size
-      ConstantInt::get(Type::getInt64Ty(SI->getContext()),
-                       Range.End-Range.Start),
+      ConstantInt::get(Type::getInt64Ty(Context), Range.End-Range.Start),
       // align
-      ConstantInt::get(Type::getInt32Ty(SI->getContext()), Range.Alignment)
+      ConstantInt::get(Type::getInt32Ty(Context), Range.Alignment)
     };
     Value *C = CallInst::Create(MemSetF, Ops, Ops+4, "", InsertPt);
     DEBUG(cerr << "Replace stores:\n";
@@ -463,7 +460,8 @@ bool MemCpyOpt::processStore(StoreInst *SI, BasicBlock::iterator& BBI) {
     BBI = BI;
 
     // Zap all the stores.
-    for (SmallVector<StoreInst*, 16>::const_iterator SI = Range.TheStores.begin(),
+    for (SmallVector<StoreInst*, 16>::const_iterator
+         SI = Range.TheStores.begin(),
          SE = Range.TheStores.end(); SI != SE; ++SI)
       (*SI)->eraseFromParent();
     ++NumMemSetInfer;