LoopVectorizer: Use abi alignment for accesses with no alignment

When we vectorize a scalar access with no alignment specified, we have to set
the target's abi alignment of the scalar access on the vectorized access.
Using the same alignment of zero would be wrong because most targets will have a
bigger abi alignment for vector types.

This probably fixes PR17878.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194876 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index bc649b3dbbce648836f6a2c36fec901e5a21f0e0..e624bb49f2a40a6d3ddd0b2a28f5ce4e4e234f98 100644 (file)
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1205,6 +1205,10 @@ void InnerLoopVectorizer::vectorizeMemoryInstruction(Instruction *Instr,
   Type *DataTy = VectorType::get(ScalarDataTy, VF);
   Value *Ptr = LI ? LI->getPointerOperand() : SI->getPointerOperand();
   unsigned Alignment = LI ? LI->getAlignment() : SI->getAlignment();
+  // An alignment of 0 means target abi alignment. We need to use the scalar's
+  // target abi alignment in such a case.
+  if (!Alignment)
+    Alignment = DL->getABITypeAlignment(ScalarDataTy);
   unsigned AddressSpace = Ptr->getType()->getPointerAddressSpace();
   unsigned ScalarAllocatedSize = DL->getTypeAllocSize(ScalarDataTy);
   unsigned VectorElementSize = DL->getTypeStoreSize(DataTy)/VF;

diff --git a/test/Transforms/LoopVectorize/align.ll b/test/Transforms/LoopVectorize/align.ll
new file mode 100644 (file)
index 0000000..84b0361
--- /dev/null
+++ b/test/Transforms/LoopVectorize/align.ll
@@ -0,0 +1,33 @@
+; RUN: opt < %s  -loop-vectorize -force-vector-unroll=1 -force-vector-width=4 -S | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.8.0"
+
+; Make sure we output the abi alignment if no alignment is specified.
+
+;CHECK-LABEL: @align
+;CHECK: load <4 x i32>* {{.*}} align  4
+;CHECK: load <4 x i32>* {{.*}} align  4
+;CHECK: store <4 x i32> {{.*}} align  4
+
+define void @align(i32* %a, i32* %b, i32* %c) nounwind uwtable ssp {
+  br label %1
+
+; <label>:1                                       ; preds = %1, %0
+  %indvars.iv = phi i64 [ 0, %0 ], [ %indvars.iv.next, %1 ]
+  %2 = getelementptr inbounds i32* %b, i64 %indvars.iv
+  %3 = load i32* %2
+  %4 = getelementptr inbounds i32* %c, i64 %indvars.iv
+  %5 = load i32* %4
+  %6 = add nsw i32 %5, %3
+  %7 = getelementptr inbounds i32* %a, i64 %indvars.iv
+  store i32 %6, i32* %7
+  %indvars.iv.next = add i64 %indvars.iv, 1
+  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
+  %exitcond = icmp eq i32 %lftr.wideiv, 128 
+  br i1 %exitcond, label %8, label %1
+
+; <label>:8                                       ; preds = %1
+  ret void
+}
+