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

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a4c1e98..98e7f40 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -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);
   }

diff --git a/llvm/test/CodeGen/PowerPC/fmf-propagation.ll b/llvm/test/CodeGen/PowerPC/fmf-propagation.ll
index 0ce4701..a62ef79 100644 (file)
--- a/llvm/test/CodeGen/PowerPC/fmf-propagation.ll
+++ b/llvm/test/CodeGen/PowerPC/fmf-propagation.ll
@@ -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) {