Index: cfe/trunk/lib/CodeGen/CGDecl.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGDecl.cpp
+++ cfe/trunk/lib/CodeGen/CGDecl.cpp
@@ -967,11 +967,12 @@
 /// FIXME We could be more clever, as we are for bzero above, and generate
 ///       memset followed by stores. It's unclear that's worth the effort.
 static llvm::Value *shouldUseMemSetToInitialize(llvm::Constant *Init,
-                                                uint64_t GlobalSize) {
+                                                uint64_t GlobalSize,
+                                                const llvm::DataLayout &DL) {
   uint64_t SizeLimit = 32;
   if (GlobalSize <= SizeLimit)
     return nullptr;
-  return llvm::isBytewiseValue(Init);
+  return llvm::isBytewiseValue(Init, DL);
 }
 
 /// Decide whether we want to split a constant structure or array store into a
@@ -1177,7 +1178,8 @@
   }
 
   // If the initializer is a repeated byte pattern, use memset.
-  llvm::Value *Pattern = shouldUseMemSetToInitialize(constant, ConstantSize);
+  llvm::Value *Pattern =
+      shouldUseMemSetToInitialize(constant, ConstantSize, CGM.getDataLayout());
   if (Pattern) {
     uint64_t Value = 0x00;
     if (!isa<llvm::UndefValue>(Pattern)) {
Index: llvm/trunk/include/llvm/Analysis/ValueTracking.h
===================================================================
--- llvm/trunk/include/llvm/Analysis/ValueTracking.h
+++ llvm/trunk/include/llvm/Analysis/ValueTracking.h
@@ -224,7 +224,7 @@
   /// 0.0 etc. If the value can't be handled with a repeated byte store (e.g.
   /// i16 0x1234), return null. If the value is entirely undef and padding,
   /// return undef.
-  Value *isBytewiseValue(Value *V);
+  Value *isBytewiseValue(Value *V, const DataLayout &DL);
 
   /// Given an aggregrate and an sequence of indices, see if the scalar value
   /// indexed is already around as a register, for example if it were inserted
Index: llvm/trunk/lib/Analysis/ValueTracking.cpp
===================================================================
--- llvm/trunk/lib/Analysis/ValueTracking.cpp
+++ llvm/trunk/lib/Analysis/ValueTracking.cpp
@@ -3166,7 +3166,7 @@
   return true;
 }
 
-Value *llvm::isBytewiseValue(Value *V) {
+Value *llvm::isBytewiseValue(Value *V, const DataLayout &DL) {
 
   // All byte-wide stores are splatable, even of arbitrary variables.
   if (V->getType()->isIntegerTy(8))
@@ -3205,7 +3205,8 @@
     else if (CFP->getType()->isDoubleTy())
       Ty = Type::getInt64Ty(Ctx);
     // Don't handle long double formats, which have strange constraints.
-    return Ty ? isBytewiseValue(ConstantExpr::getBitCast(CFP, Ty)) : nullptr;
+    return Ty ? isBytewiseValue(ConstantExpr::getBitCast(CFP, Ty), DL)
+              : nullptr;
   }
 
   // We can handle constant integers that are multiple of 8 bits.
@@ -3233,20 +3234,20 @@
   if (ConstantDataSequential *CA = dyn_cast<ConstantDataSequential>(C)) {
     Value *Val = UndefInt8;
     for (unsigned I = 0, E = CA->getNumElements(); I != E; ++I)
-      if (!(Val = Merge(Val, isBytewiseValue(CA->getElementAsConstant(I)))))
+      if (!(Val = Merge(Val, isBytewiseValue(CA->getElementAsConstant(I), DL))))
         return nullptr;
     return Val;
   }
 
   if (isa<ConstantVector>(C)) {
     Constant *Splat = cast<ConstantVector>(C)->getSplatValue();
-    return Splat ? isBytewiseValue(Splat) : nullptr;
+    return Splat ? isBytewiseValue(Splat, DL) : nullptr;
   }
 
   if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) {
     Value *Val = UndefInt8;
     for (unsigned I = 0, E = C->getNumOperands(); I != E; ++I)
-      if (!(Val = Merge(Val, isBytewiseValue(C->getOperand(I)))))
+      if (!(Val = Merge(Val, isBytewiseValue(C->getOperand(I), DL))))
         return nullptr;
     return Val;
   }
Index: llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
+++ llvm/trunk/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
@@ -450,7 +450,7 @@
   // turned into a memset of i8 -1, assuming that all the consecutive bytes
   // are stored.  A store of i32 0x01020304 can never be turned into a memset,
   // but it can be turned into memset_pattern if the target supports it.
-  Value *SplatValue = isBytewiseValue(StoredVal);
+  Value *SplatValue = isBytewiseValue(StoredVal, *DL);
   Constant *PatternValue = nullptr;
 
   // Note: memset and memset_pattern on unordered-atomic is yet not supported
@@ -627,7 +627,7 @@
     Constant *FirstPatternValue = nullptr;
 
     if (For == ForMemset::Yes)
-      FirstSplatValue = isBytewiseValue(FirstStoredVal);
+      FirstSplatValue = isBytewiseValue(FirstStoredVal, *DL);
     else
       FirstPatternValue = getMemSetPatternValue(FirstStoredVal, DL);
 
@@ -660,7 +660,7 @@
       Constant *SecondPatternValue = nullptr;
 
       if (For == ForMemset::Yes)
-        SecondSplatValue = isBytewiseValue(SecondStoredVal);
+        SecondSplatValue = isBytewiseValue(SecondStoredVal, *DL);
       else
         SecondPatternValue = getMemSetPatternValue(SecondStoredVal, DL);
 
@@ -880,7 +880,7 @@
     Value *StoredVal, Instruction *TheStore,
     SmallPtrSetImpl<Instruction *> &Stores, const SCEVAddRecExpr *Ev,
     const SCEV *BECount, bool NegStride, bool IsLoopMemset) {
-  Value *SplatValue = isBytewiseValue(StoredVal);
+  Value *SplatValue = isBytewiseValue(StoredVal, *DL);
   Constant *PatternValue = nullptr;
 
   if (!SplatValue)
Index: llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -412,7 +412,7 @@
       if (!NextStore->isSimple()) break;
 
       // Check to see if this stored value is of the same byte-splattable value.
-      Value *StoredByte = isBytewiseValue(NextStore->getOperand(0));
+      Value *StoredByte = isBytewiseValue(NextStore->getOperand(0), DL);
       if (isa<UndefValue>(ByteVal) && StoredByte)
         ByteVal = StoredByte;
       if (ByteVal != StoredByte)
@@ -749,7 +749,7 @@
   // byte at a time like "0" or "-1" or any width, as well as things like
   // 0xA0A0A0A0 and 0.0.
   auto *V = SI->getOperand(0);
-  if (Value *ByteVal = isBytewiseValue(V)) {
+  if (Value *ByteVal = isBytewiseValue(V, DL)) {
     if (Instruction *I = tryMergingIntoMemset(SI, SI->getPointerOperand(),
                                               ByteVal)) {
       BBI = I->getIterator(); // Don't invalidate iterator.
@@ -1229,7 +1229,8 @@
   // If copying from a constant, try to turn the memcpy into a memset.
   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(M->getSource()))
     if (GV->isConstant() && GV->hasDefinitiveInitializer())
-      if (Value *ByteVal = isBytewiseValue(GV->getInitializer())) {
+      if (Value *ByteVal = isBytewiseValue(GV->getInitializer(),
+                                           M->getModule()->getDataLayout())) {
         IRBuilder<> Builder(M);
         Builder.CreateMemSet(M->getRawDest(), ByteVal, M->getLength(),
                              M->getDestAlignment(), false);