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[LV] Ensure reverse interleaved group GEPs remain uniform

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For uniform instructions, we're only required to generate a scalar value for
the first vector lane of each unroll iteration. Thus, if we have a reverse
interleaved group, computing the member index off the scalar GEP corresponding
to the last vector lane of its pointer operand technically makes the GEP
non-uniform. We should compute the member index off the first scalar GEP
instead.

I've added the updated member index computation to the existing reverse
interleaved group test.

llvm-svn: 280497
This commit is contained in:
Matthew Simpson 2016-09-02 16:19:22 +00:00
parent c30204881e
commit a8cb85d1b1
2 changed files with 19 additions and 3 deletions
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12
lib/Transforms/Vectorize/LoopVectorize.cpp
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@ -2600,8 +2600,18 @@ void InnerLoopVectorizer::vectorizeInterleaveGroup(Instruction *Instr) {
setDebugLocFromInst(Builder, Ptr);
SmallVector<Value *, 2> NewPtrs;
unsigned Index = Group->getIndex(Instr);
// If the group is reverse, adjust the index to refer to the last vector lane
// instead of the first. We adjust the index from the first vector lane,
// rather than directly getting the pointer for lane VF - 1, because the
// pointer operand of the interleaved access is supposed to be uniform. For
// uniform instructions, we're only required to generate a value for the
// first vector lane in each unroll iteration.
if (Group->isReverse())
Index += (VF - 1) * Group->getFactor();
for (unsigned Part = 0; Part < UF; Part++) {
Value *NewPtr = getScalarValue(Ptr, Part, Group->isReverse() ? VF - 1 : 0);
Value *NewPtr = getScalarValue(Ptr, Part, 0);
// Notice current instruction could be any index. Need to adjust the address
// to the member of index 0.

10
test/Transforms/LoopVectorize/interleaved-accesses.ll
View File

@ -244,17 +244,23 @@ for.body: ; preds = %for.body, %entry
; }
; CHECK-LABEL: @test_reversed_load2_store2(
; CHECK: %wide.vec = load <8 x i32>, <8 x i32>* {{.*}}, align 4
; CHECK: %[[G0:.+]] = getelementptr inbounds %struct.ST2, %struct.ST2* %A, i64 %offset.idx, i32 0
; CHECK: %[[G1:.+]] = getelementptr i32, i32* %[[G0]], i64 -6
; CHECK: %[[B0:.+]] = bitcast i32* %[[G1]] to <8 x i32>*
; CHECK: %wide.vec = load <8 x i32>, <8 x i32>* %[[B0]], align 4
; CHECK: shufflevector <8 x i32> %wide.vec, <8 x i32> undef, <4 x i32> <i32 0, i32 2, i32 4, i32 6>
; CHECK: shufflevector <4 x i32> {{.*}}, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
; CHECK: shufflevector <8 x i32> %wide.vec, <8 x i32> undef, <4 x i32> <i32 1, i32 3, i32 5, i32 7>
; CHECK: shufflevector <4 x i32> {{.*}}, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
; CHECK: add nsw <4 x i32>
; CHECK: sub nsw <4 x i32>
; CHECK: %[[G2:.+]] = getelementptr inbounds %struct.ST2, %struct.ST2* %B, i64 %offset.idx, i32 1
; CHECK: %[[G3:.+]] = getelementptr i32, i32* %[[G2]], i64 -7
; CHECK: %[[B1:.+]] = bitcast i32* %[[G3]] to <8 x i32>*
; CHECK: shufflevector <4 x i32> {{.*}}, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
; CHECK: shufflevector <4 x i32> {{.*}}, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
; CHECK: %interleaved.vec = shufflevector <4 x i32> {{.*}}, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
; CHECK: store <8 x i32> %interleaved.vec, <8 x i32>* %{{.*}}, align 4
; CHECK: store <8 x i32> %interleaved.vec, <8 x i32>* %[[B1]], align 4
%struct.ST2 = type { i32, i32 }