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[DAGCombiner] Add general constant vector support to (shl (mul x, c1), c2) -> (mul x, c1 << c2)

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We already supported scalar constant / splatted constant vector - now accepts any (non opaque) constant scalar / vector

llvm-svn: 284607
This commit is contained in:
Simon Pilgrim 2016-10-19 15:59:28 +00:00
parent 9484732ba1
commit 4b04830ee0
2 changed files with 6 additions and 6 deletions
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11
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -4678,11 +4678,12 @@ SDValue DAGCombiner::visitSHL(SDNode *N) {
}
// fold (shl (mul x, c1), c2) -> (mul x, c1 << c2)
if (N1C && N0.getOpcode() == ISD::MUL && N0.getNode()->hasOneUse()) {
if (ConstantSDNode *N0C1 = isConstOrConstSplat(N0.getOperand(1))) {
if (SDValue Folded =
DAG.FoldConstantArithmetic(ISD::SHL, SDLoc(N1), VT, N0C1, N1C))
return DAG.getNode(ISD::MUL, SDLoc(N), VT, N0.getOperand(0), Folded);
if (N0.getOpcode() == ISD::MUL && N0.getNode()->hasOneUse()) {
if (isConstantOrConstantVector(N1, /* No Opaques */ true) &&
isConstantOrConstantVector(N0.getOperand(1), /* No Opaques */ true)) {
SDValue Shl = DAG.getNode(ISD::SHL, SDLoc(N1), VT, N0.getOperand(1), N1);
AddToWorklist(Shl.getNode());
return DAG.getNode(ISD::MUL, SDLoc(N), VT, N0.getOperand(0), Shl);
}
}

1
test/CodeGen/X86/combine-shl.ll
View File

@ -572,7 +572,6 @@ define <4 x i32> @combine_vec_shl_mul1(<4 x i32> %x) {
; AVX-LABEL: combine_vec_shl_mul1:
; AVX: # BB#0:
; AVX-NEXT: vpmulld {{.*}}(%rip), %xmm0, %xmm0
; AVX-NEXT: vpsllvd {{.*}}(%rip), %xmm0, %xmm0
; AVX-NEXT: retq
%1 = mul <4 x i32> %x, <i32 5, i32 6, i32 7, i32 8>
%2 = shl <4 x i32> %1, <i32 1, i32 2, i32 3, i32 4>