[LV] Preserve inbounds on created GEPs

Summary:
This is a fix for PR23997.

The loop vectorizer is not preserving the inbounds property of GEPs that it creates.
This is inhibiting some optimizations. This patch preserves the inbounds property in
the case where a load/store is being fed by an inbounds GEP.

Reviewers: mkuper, javed.absar, hsaito

Reviewed By: hsaito

Subscribers: dcaballe, hsaito, llvm-commits

Differential Revision: https://reviews.llvm.org/D46191

llvm-svn: 331269

1 files changed, 22 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 8778a2d5f2d..4a80dc08a46 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2254,6 +2254,10 @@ void InnerLoopVectorizer::vectorizeInterleaveGroup(Instruction *Instr) {
   if (Group->isReverse())
     Index += (VF - 1) * Group->getFactor();
 
+  bool InBounds = false;
+  if (auto *gep = dyn_cast<GetElementPtrInst>(Ptr->stripPointerCasts()))
+    InBounds = gep->isInBounds();
+
   for (unsigned Part = 0; Part < UF; Part++) {
     Value *NewPtr = getOrCreateScalarValue(Ptr, {Part, 0});
 
@@ -2269,6 +2273,8 @@ void InnerLoopVectorizer::vectorizeInterleaveGroup(Instruction *Instr) {
     //       A[i+2] = c;     // Member of index 2 (Current instruction)
     // Current pointer is pointed to A[i+2], adjust it to A[i].
     NewPtr = Builder.CreateGEP(NewPtr, Builder.getInt32(-Index));
+    if (InBounds)
+      cast<GetElementPtrInst>(NewPtr)->setIsInBounds(true);
 
     // Cast to the vector pointer type.
     NewPtrs.push_back(Builder.CreateBitCast(NewPtr, PtrTy));
@@ -2405,17 +2411,30 @@ void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr,
   if (isMaskRequired)
     Mask = *BlockInMask;
 
+  bool InBounds = false;
+  if (auto *gep = dyn_cast<GetElementPtrInst>(
+          getLoadStorePointerOperand(Instr)->stripPointerCasts()))
+    InBounds = gep->isInBounds();
+
   const auto CreateVecPtr = [&](unsigned Part, Value *Ptr) -> Value * {
     // Calculate the pointer for the specific unroll-part.
-    Value *PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF));
+    GetElementPtrInst *PartPtr = nullptr;
 
     if (Reverse) {
       // If the address is consecutive but reversed, then the
       // wide store needs to start at the last vector element.
-      PartPtr = Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF));
-      PartPtr = Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF));
+      PartPtr = cast<GetElementPtrInst>(
+          Builder.CreateGEP(Ptr, Builder.getInt32(-Part * VF)));
+      PartPtr->setIsInBounds(InBounds);
+      PartPtr = cast<GetElementPtrInst>(
+          Builder.CreateGEP(PartPtr, Builder.getInt32(1 - VF)));
+      PartPtr->setIsInBounds(InBounds);
       if (isMaskRequired) // Reverse of a null all-one mask is a null mask.
         Mask[Part] = reverseVector(Mask[Part]);
+    } else {
+      PartPtr = cast<GetElementPtrInst>(
+          Builder.CreateGEP(Ptr, Builder.getInt32(Part * VF)));
+      PartPtr->setIsInBounds(InBounds);
     }
 
     return Builder.CreateBitCast(PartPtr, DataTy->getPointerTo(AddressSpace));