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[DAGCombiner] Add vector support to (sub -1, x) -> (xor x, -1) canonicalization 

Improves commutation potential

llvm-svn: 284113
This commit is contained in:
Simon Pilgrim 2016-10-13 12:05:20 +00:00
parent bb51662d8d
commit 833b8a2071
2 changed files with 14 additions and 4 deletions
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13
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -863,6 +863,17 @@ static bool isOneConstantOrOneSplatConstant(SDValue N) {
return false; return false;
} }
// Determines if it is a constant integer of all ones or a splatted vector of a
// constant integer of all ones (with no undefs).
// Do not permit build vector implicit truncation.
static bool isAllOnesConstantOrAllOnesSplatConstant(SDValue N) {
unsigned BitWidth = N.getScalarValueSizeInBits();
if (ConstantSDNode *Splat = isConstOrConstSplat(N))
return Splat->isAllOnesValue() &&
Splat->getAPIntValue().getBitWidth() == BitWidth;
return false;
}
SDValue DAGCombiner::ReassociateOps(unsigned Opc, const SDLoc &DL, SDValue N0, SDValue DAGCombiner::ReassociateOps(unsigned Opc, const SDLoc &DL, SDValue N0,
SDValue N1) { SDValue N1) {
EVT VT = N0.getValueType(); EVT VT = N0.getValueType();
@ -1938,7 +1949,7 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
} }
// Canonicalize (sub -1, x) -> ~x, i.e. (xor x, -1) // Canonicalize (sub -1, x) -> ~x, i.e. (xor x, -1)
if (isAllOnesConstant(N0)) if (isAllOnesConstantOrAllOnesSplatConstant(N0))
return DAG.getNode(ISD::XOR, DL, VT, N1, N0); return DAG.getNode(ISD::XOR, DL, VT, N1, N0);
// fold A-(A-B) -> B // fold A-(A-B) -> B

5
llvm/test/CodeGen/X86/combine-sub.ll
View File

@ -50,14 +50,13 @@ define <4 x i32> @combine_vec_sub_negone(<4 x i32> %x) {
; SSE-LABEL: combine_vec_sub_negone: ; SSE-LABEL: combine_vec_sub_negone:
; SSE: # BB#0: ; SSE: # BB#0:
; SSE-NEXT: pcmpeqd %xmm1, %xmm1 ; SSE-NEXT: pcmpeqd %xmm1, %xmm1
; SSE-NEXT: psubd %xmm0, %xmm1 ; SSE-NEXT: pxor %xmm1, %xmm0
; SSE-NEXT: movdqa %xmm1, %xmm0
; SSE-NEXT: retq ; SSE-NEXT: retq
; ;
; AVX-LABEL: combine_vec_sub_negone: ; AVX-LABEL: combine_vec_sub_negone:
; AVX: # BB#0: ; AVX: # BB#0:
; AVX-NEXT: vpcmpeqd %xmm1, %xmm1, %xmm1 ; AVX-NEXT: vpcmpeqd %xmm1, %xmm1, %xmm1
; AVX-NEXT: vpsubd %xmm0, %xmm1, %xmm0 ; AVX-NEXT: vpxor %xmm1, %xmm0, %xmm0
; AVX-NEXT: retq ; AVX-NEXT: retq
%1 = sub <4 x i32> <i32 -1, i32 -1, i32 -1, i32 -1>, %x %1 = sub <4 x i32> <i32 -1, i32 -1, i32 -1, i32 -1>, %x
ret <4 x i32> %1 ret <4 x i32> %1