[PATCH] D142626: AMDGPU: Factor out fneg fold predicate function

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: AMDGPU, foad, Pierre-vh, rampitec, sebastian-ne.
Herald added subscribers: kosarev, StephenFan, kerbowa, hiraditya, tpr, dstuttard, yaxunl, jvesely, kzhuravl.
Herald added a project: All.
arsenm requested review of this revision.
Herald added a subscriber: wdng.
Herald added a project: LLVM.

https://reviews.llvm.org/D142626

Files:
  llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
  llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h


Index: llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h
+++ llvm/lib/Target/AMDGPU/AMDGPUISelLowering.h
@@ -156,6 +156,7 @@
     return Val.getOpcode() == ISD::BITCAST ? Val.getOperand(0) : Val;
   }
 
+  static bool shouldFoldFNegIntoSrc(SDNode *FNeg, SDValue FNegSrc);
   static bool allUsesHaveSourceMods(const SDNode *N,
                                     unsigned CostThreshold = 4);
   bool isFAbsFree(EVT VT) const override;
Index: llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
+++ llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp
@@ -3862,12 +3862,9 @@
   }
 }
 
-SDValue AMDGPUTargetLowering::performFNegCombine(SDNode *N,
-                                                 DAGCombinerInfo &DCI) const {
-  SelectionDAG &DAG = DCI.DAG;
-  SDValue N0 = N->getOperand(0);
-  EVT VT = N->getValueType(0);
-
+/// \return true if it's profitable to try to push an fneg into its source
+/// instruction.
+bool AMDGPUTargetLowering::shouldFoldFNegIntoSrc(SDNode *N, SDValue N0) {
   unsigned Opc = N0.getOpcode();
 
   // If the input has multiple uses and we can either fold the negate down, or
@@ -3878,13 +3875,27 @@
     // This may be able to fold into the source, but at a code size cost. Don't
     // fold if the fold into the user is free.
     if (allUsesHaveSourceMods(N, 0))
-      return SDValue();
+      return false;
   } else {
     if (fnegFoldsIntoOp(Opc) &&
         (allUsesHaveSourceMods(N) || !allUsesHaveSourceMods(N0.getNode())))
-      return SDValue();
+      return false;
   }
 
+  return true;
+}
+
+SDValue AMDGPUTargetLowering::performFNegCombine(SDNode *N,
+                                                 DAGCombinerInfo &DCI) const {
+  SelectionDAG &DAG = DCI.DAG;
+  SDValue N0 = N->getOperand(0);
+  EVT VT = N->getValueType(0);
+
+  unsigned Opc = N0.getOpcode();
+
+  if (!shouldFoldFNegIntoSrc(N, N0))
+    return SDValue();
+
   SDLoc SL(N);
   switch (Opc) {
   case ISD::FADD: {


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