Remove TargetBaseAlign. Keep alignment for stack adjustments.

Summary:
TargetBaseAlign is no longer required since LSV checks if target allows misaligned accesses.
A constant defining a base alignment is still needed for stack accesses where alignment can be adjusted.

Reviewers: llvm-commits, jlebar

Subscribers: mzolotukhin, arsenm

Differential Revision: https://reviews.llvm.org/D22936

llvm-svn: 277038

1 files changed, 9 insertions, 10 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp b/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
index 0d6ae4c72fd..3c7657bc433 100644
--- a/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
@@ -40,9 +40,8 @@ STATISTIC(NumScalarsVectorized, "Number of scalar accesses vectorized");
 
 namespace {
 
-// TODO: Remove this
-static const unsigned TargetBaseAlign = 4;
-
+// FIXME: Assuming stack alignment of 4 is always good enough
+static const unsigned StackAdjustedAlignment = 4;
 typedef SmallVector<Instruction *, 8> InstrList;
 typedef MapVector<Value *, InstrList> InstrListMap;
 
@@ -798,8 +797,8 @@ bool Vectorizer::vectorizeStoreChain(
     // so we can cheat and change it!
     Value *V = GetUnderlyingObject(S0->getPointerOperand(), DL);
     if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(V)) {
-      AI->setAlignment(TargetBaseAlign);
-      Alignment = TargetBaseAlign;
+      AI->setAlignment(StackAdjustedAlignment);
+      Alignment = StackAdjustedAlignment;
     } else {
       return false;
     }
@@ -948,8 +947,8 @@ bool Vectorizer::vectorizeLoadChain(
     // so we can cheat and change it!
     Value *V = GetUnderlyingObject(L0->getPointerOperand(), DL);
     if (AllocaInst *AI = dyn_cast_or_null<AllocaInst>(V)) {
-      AI->setAlignment(TargetBaseAlign);
-      Alignment = TargetBaseAlign;
+      AI->setAlignment(StackAdjustedAlignment);
+      Alignment = StackAdjustedAlignment;
     } else {
       return false;
     }
@@ -1029,10 +1028,10 @@ bool Vectorizer::vectorizeLoadChain(
 
 bool Vectorizer::accessIsMisaligned(unsigned SzInBytes, unsigned AddressSpace,
                                     unsigned Alignment) {
+  if (Alignment % SzInBytes == 0)
+    return false;
   bool Fast = false;
   bool Allows = TTI.allowsMisalignedMemoryAccesses(SzInBytes * 8, AddressSpace,
                                                    Alignment, &Fast);
-  // TODO: Remove TargetBaseAlign
-  return !(Allows && Fast) && (Alignment % SzInBytes) != 0 &&
-         (Alignment % TargetBaseAlign) != 0;
+  return !Allows || !Fast;
 }