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{DAGCombiner] Fold (rot x, 0) -> x 

llvm-svn: 307184
This commit is contained in:
Simon Pilgrim 2017-07-05 18:27:11 +00:00
parent 49123d4bb0
commit ac78daf517
2 changed files with 4 additions and 1 deletions
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4
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -5273,6 +5273,10 @@ SDValue DAGCombiner::visitRotate(SDNode *N) {
SDValue N1 = N->getOperand(1);
EVT VT = N->getValueType(0);
// fold (rot x, 0) -> x
if (isNullConstantOrNullSplatConstant(N1))
return N0;
// fold (rot* x, (trunc (and y, c))) -> (rot* x, (and (trunc y), (trunc c))).
if (N1.getOpcode() == ISD::TRUNCATE &&
N1.getOperand(0).getOpcode() == ISD::AND) {

1
llvm/test/CodeGen/X86/combine-rotates.ll
View File

@ -59,7 +59,6 @@ define <4 x i32> @combine_vec_rot_rot_splat(<4 x i32> %x) {
define <4 x i32> @combine_vec_rot_rot_splat_zero(<4 x i32> %x) {
; XOP-LABEL: combine_vec_rot_rot_splat_zero:
; XOP: # BB#0:
; XOP-NEXT: vprotd $0, %xmm0, %xmm0
; XOP-NEXT: retq
;
; AVX512-LABEL: combine_vec_rot_rot_splat_zero: