[llvm] r362439 - Propagate fmf for setcc/select folds

[Michael Berg via llvm-commits]

Author: mcberg2017
Date: Mon Jun  3 12:12:15 2019
New Revision: 362439

URL: http://llvm.org/viewvc/llvm-project?rev=362439&view=rev
Log:
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

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/PowerPC/fmf-propagation.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=362439&r1=362438&r2=362439&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Mon Jun  3 12:12:15 2019
@@ -7941,9 +7941,16 @@ SDValue DAGCombiner::visitSELECT(SDNode
     }
 
     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);
   }

Modified: llvm/trunk/test/CodeGen/PowerPC/fmf-propagation.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/fmf-propagation.ll?rev=362439&r1=362438&r2=362439&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/fmf-propagation.ll (original)
+++ llvm/trunk/test/CodeGen/PowerPC/fmf-propagation.ll Mon Jun  3 12:12:15 2019
@@ -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) {