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

1 files changed, 10 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a4c1e9886ae..98e7f4055e9 100644
--- 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);
   }