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Propagate fmf for setcc/select folds 

Summary: This change facilitates propagating fmf which was placed on setcc from fcmp through folds with selects so that back ends can model this path for arithmetic folds on selects in SDAG.

Reviewers: qcolombet, spatel

Reviewed By: qcolombet

Subscribers: nemanjai, jsji

Differential Revision: https://reviews.llvm.org/D62552

llvm-svn: 362439
This commit is contained in:
Michael Berg 2019-06-03 19:12:15 +00:00
parent bad43d8f49
commit 0b7f98da65
2 changed files with 12 additions and 5 deletions
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13
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -7941,9 +7941,16 @@ SDValue DAGCombiner::visitSELECT(SDNode *N) {
}
if (TLI.isOperationLegal(ISD::SELECT_CC, VT) ||
(!LegalOperations && TLI.isOperationLegalOrCustom(ISD::SELECT_CC, VT)))
return DAG.getNode(ISD::SELECT_CC, DL, VT, Cond0, Cond1, N1, N2,
N0.getOperand(2));
(!LegalOperations &&
TLI.isOperationLegalOrCustom(ISD::SELECT_CC, VT))) {
// Any flags available in a select/setcc fold will be on the setcc as they
// migrated from fcmp
const SDNodeFlags Flags = N0.getNode()->getFlags();
SDValue SelectNode = DAG.getNode(ISD::SELECT_CC, DL, VT, Cond0, Cond1, N1,
N2, N0.getOperand(2));
SelectNode->setFlags(Flags);
return SelectNode;
}
return SimplifySelect(DL, N0, N1, N2);
}

4
llvm/test/CodeGen/PowerPC/fmf-propagation.ll
View File

@ -375,11 +375,11 @@ define float @sqrt_fast(float %x) {
; fcmp can have fast-math-flags.
; FMFDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fcmp_nnan:'
; FMFDEBUG: select_cc {{t[0-9]+}}
; FMFDEBUG: select_cc nnan {{t[0-9]+}}
; FMFDEBUG: Type-legalized selection DAG: %bb.0 'fcmp_nnan:'
; GLOBALDEBUG-LABEL: Optimized lowered selection DAG: %bb.0 'fcmp_nnan:'
; GLOBALDEBUG: select_cc {{t[0-9]+}}
; GLOBALDEBUG: select_cc nnan {{t[0-9]+}}
; GLOBALDEBUG: Type-legalized selection DAG: %bb.0 'fcmp_nnan:'
define double @fcmp_nnan(double %a, double %y, double %z) {