[PATCH] D107551: [DAGCombine] Add node level checks for fp-contract and fp-ninf in visitFMULForFMADistributiveCombine().

[Abinav Puthan Purayil via Phabricator via llvm-commits]

abinavpp created this revision.
Herald added subscribers: ecnelises, kerbowa, hiraditya, nhaehnle, jvesely.
abinavpp requested review of this revision.
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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D107551

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/AMDGPU/fma.ll


Index: llvm/test/CodeGen/AMDGPU/fma.ll
===================================================================
--- llvm/test/CodeGen/AMDGPU/fma.ll
+++ llvm/test/CodeGen/AMDGPU/fma.ll
@@ -144,3 +144,11 @@
   store float %tmp10, float addrspace(1)* %gep.out
   ret void
 }
+
+; FUNC-LABEL: {{^}}fold_fmul_distributive:
+; GFX906: v_fmac_f32_e32 v0, v1, v0
+define float @fold_fmul_distributive(float %x, float %y) {
+  %fadd = fadd ninf float %y, 1.0
+  %fmul = fmul contract float %fadd, %x
+  ret float %fmul
+}
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -13002,6 +13002,20 @@
   return DAG.getBuildVector(VT, DL, Ops);
 }
 
+// Returns true if floating point contraction is allowed on the FMUL-SDValue
+// `N`
+bool isContractableFMUL(const TargetOptions &Options, SDValue N) {
+  assert(N.getOpcode() == ISD::FMUL);
+
+  return Options.AllowFPOpFusion == FPOpFusion::Fast || Options.UnsafeFPMath ||
+         N->getFlags().hasAllowContract();
+}
+
+// Return true if `N` can assume no infinities involved in it's computation.
+bool hasNoInfs(const TargetOptions &Options, SDValue N) {
+  return Options.NoInfsFPMath || N.getNode()->getFlags().hasNoInfs();
+}
+
 /// Try to perform FMA combining on a given FADD node.
 SDValue DAGCombiner::visitFADDForFMACombine(SDNode *N) {
   SDValue N0 = N->getOperand(0);
@@ -13537,12 +13551,13 @@
 
   // The transforms below are incorrect when x == 0 and y == inf, because the
   // intermediate multiplication produces a nan.
-  if (!Options.NoInfsFPMath)
+  SDValue FAdd = N0.getOpcode() == ISD::FADD ? N0 : N1;
+  if (!hasNoInfs(Options, FAdd))
     return SDValue();
 
   // Floating-point multiply-add without intermediate rounding.
   bool HasFMA =
-      (Options.AllowFPOpFusion == FPOpFusion::Fast || Options.UnsafeFPMath) &&
+      isContractableFMUL(Options, SDValue(N, 0)) &&
       TLI.isFMAFasterThanFMulAndFAdd(DAG.getMachineFunction(), VT) &&
       (!LegalOperations || TLI.isOperationLegalOrCustom(ISD::FMA, VT));
 


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