[SLP] Pass in correct alignment when query memory access cost

This patch fixes bug https://llvm.org/bugs/show_bug.cgi?id=27897.

When query memory access cost, current SLP always passes in alignment value of 1 (unaligned), so it gets a very high cost of scalar memory access, and wrongly vectorize memory loads in the test case.

It can be fixed by simply giving correct alignment.

llvm-svn: 271333

1 files changed, 8 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 30da577d0bd..57824434b1b 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -1726,16 +1726,20 @@ int BoUpSLP::getEntryCost(TreeEntry *E) {
     }
     case Instruction::Load: {
       // Cost of wide load - cost of scalar loads.
+      unsigned alignment = dyn_cast<LoadInst>(VL0)->getAlignment();
       int ScalarLdCost = VecTy->getNumElements() *
-      TTI->getMemoryOpCost(Instruction::Load, ScalarTy, 1, 0);
-      int VecLdCost = TTI->getMemoryOpCost(Instruction::Load, VecTy, 1, 0);
+            TTI->getMemoryOpCost(Instruction::Load, ScalarTy, alignment, 0);
+      int VecLdCost = TTI->getMemoryOpCost(Instruction::Load,
+                                           VecTy, alignment, 0);
       return VecLdCost - ScalarLdCost;
     }
     case Instruction::Store: {
       // We know that we can merge the stores. Calculate the cost.
+      unsigned alignment = dyn_cast<StoreInst>(VL0)->getAlignment();
       int ScalarStCost = VecTy->getNumElements() *
-      TTI->getMemoryOpCost(Instruction::Store, ScalarTy, 1, 0);
-      int VecStCost = TTI->getMemoryOpCost(Instruction::Store, VecTy, 1, 0);
+            TTI->getMemoryOpCost(Instruction::Store, ScalarTy, alignment, 0);
+      int VecStCost = TTI->getMemoryOpCost(Instruction::Store,
+                                           VecTy, alignment, 0);
       return VecStCost - ScalarStCost;
     }
     case Instruction::Call: {