LoopVectorize: Scalarize padded types

This patch disables memory-instruction vectorization for types that need padding
bytes, e.g., x86_fp80 has 10 bytes store size with 6 bytes padding in darwin on
x86_64. Because the load/store vectorization is performed by the bit casting to
a packed vector, which has incompatible memory layout due to the lack of padding
bytes, the present vectorizer produces inconsistent result for memory
instructions of those types.
This patch checks an equality of the AllocSize of a scalar type and allocated
size for each vector element, to ensure that there is no padding bytes and the
array can be read/written using vector operations.

Patch by Daisuke Takahashi!

Fixes PR15758.

llvm-svn: 180196

1 files changed, 9 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index ac0925df2a0..56a9a2d3d45 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -956,6 +956,12 @@ void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr,
   Value *Ptr = LI ? LI->getPointerOperand() : SI->getPointerOperand();
   unsigned Alignment = LI ? LI->getAlignment() : SI->getAlignment();
 
+  unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ScalarDataTy);
+  unsigned VectorElementSize = DL->getTypeStoreSize(DataTy)/VF;
+
+  if (ScalarAllocatedSize != VectorElementSize)
+    return scalarizeInstruction(Instr);
+
   // If the pointer is loop invariant or if it is non consecutive,
   // scalarize the load.
   int Stride = Legal->isConsecutivePtr(Ptr);
@@ -3558,7 +3564,9 @@ LoopVectorizationCostModel::getInstructionCost(Instruction *I, unsigned VF) {
     // Scalarized loads/stores.
     int Stride = Legal->isConsecutivePtr(Ptr);
     bool Reverse = Stride < 0;
-    if (0 == Stride) {
+    unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ValTy);
+    unsigned VectorElementSize = DL->getTypeStoreSize(VectorTy)/VF;
+    if (0 == Stride || ScalarAllocatedSize != VectorElementSize) {
       unsigned Cost = 0;
       // The cost of extracting from the value vector and pointer vector.
       Type *PtrTy = ToVectorTy(Ptr->getType(), VF);