2 files changed, 33 insertions, 4 deletions
diff --git a/llvm/lib/VMCore/ConstantFold.cpp b/llvm/lib/VMCore/ConstantFold.cpp
index ddd55878cb9..24b78ae969a 100644
--- a/llvm/lib/VMCore/ConstantFold.cpp
+++ b/llvm/lib/VMCore/ConstantFold.cpp
@@ -415,9 +415,38 @@ Constant *llvm::ConstantFoldCastInstruction(LLVMContext &Context,
       return ConstantPointerNull::get(cast<PointerType>(DestTy));
     return 0;                   // Other pointer types cannot be casted
   case Instruction::PtrToInt:   // always treated as unsigned
-    if (V->isNullValue())       // is it a null pointer value?
+    // Is it a null pointer value?
+    if (V->isNullValue())
       return ConstantInt::get(DestTy, 0);
-    return 0;                   // Other pointer types cannot be casted
+    // If this is a sizeof of an array or vector, pull out a multiplication
+    // by the element size to expose it to subsequent folding.
+    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
+      if (CE->getOpcode() == Instruction::GetElementPtr &&
+          CE->getNumOperands() == 2 &&
+          CE->getOperand(0)->isNullValue())
+        if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
+          if (CI->isOne()) {
+            const Type *Ty =
+              cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
+            if (const ArrayType *ATy = dyn_cast<ArrayType>(Ty)) {
+              Constant *N = ConstantInt::get(DestTy, ATy->getNumElements());
+              Constant *E = ConstantExpr::getSizeOf(ATy->getElementType());
+              E = ConstantExpr::getCast(CastInst::getCastOpcode(E, false,
+                                                                DestTy, false),
+                                        E, DestTy);
+              return ConstantExpr::getMul(N, E);
+            }
+            if (const VectorType *VTy = dyn_cast<VectorType>(Ty)) {
+              Constant *N = ConstantInt::get(DestTy, VTy->getNumElements());
+              Constant *E = ConstantExpr::getSizeOf(VTy->getElementType());
+              E = ConstantExpr::getCast(CastInst::getCastOpcode(E, false,
+                                                                DestTy, false),
+                                        E, DestTy);
+              return ConstantExpr::getMul(N, E);
+            }
+          }
+    // Other pointer types cannot be casted
+    return 0;
   case Instruction::UIToFP:
   case Instruction::SIToFP:
     if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
diff --git a/llvm/lib/VMCore/Constants.cpp b/llvm/lib/VMCore/Constants.cpp
index 436083f62b0..9e1154e95e3 100644
--- a/llvm/lib/VMCore/Constants.cpp
+++ b/llvm/lib/VMCore/Constants.cpp
@@ -1479,10 +1479,10 @@ Constant* ConstantExpr::getSizeOf(const Type* Ty) {
 }
 
 Constant* ConstantExpr::getAlignOf(const Type* Ty) {
-  // alignof is implemented as: (i64) gep ({i8,Ty}*)null, 0, 1
+  // alignof is implemented as: (i64) gep ({i1,Ty}*)null, 0, 1
   // Note that a non-inbounds gep is used, as null isn't within any object.
   const Type *AligningTy = StructType::get(Ty->getContext(),
-                                   Type::getInt8Ty(Ty->getContext()), Ty, NULL);
+                                   Type::getInt1Ty(Ty->getContext()), Ty, NULL);
   Constant *NullPtr = Constant::getNullValue(AligningTy->getPointerTo());
   Constant *Zero = ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 0);
   Constant *One = ConstantInt::get(Type::getInt32Ty(Ty->getContext()), 1);