[PATCH] D63141: [DAGCombine] GetNegatedExpression - add FMA\FMAD support

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: arsenm, spatel.
Herald added subscribers: nhaehnle, wdng, jvesely.
Herald added a project: LLVM.

If the accumulator and either of the multiply operands are negateable then we can we negate the entire expression.


Repository:
  rL LLVM

https://reviews.llvm.org/D63141

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/AMDGPU/fneg-combines.ll


Index: test/CodeGen/AMDGPU/fneg-combines.ll
===================================================================
--- test/CodeGen/AMDGPU/fneg-combines.ll
+++ test/CodeGen/AMDGPU/fneg-combines.ll
@@ -1230,13 +1230,9 @@
 ; GCN: {{buffer|flat}}_load_dword [[A:v[0-9]+]]
 ; GCN: {{buffer|flat}}_load_dword [[B:v[0-9]+]]
 ; GCN: {{buffer|flat}}_load_dword [[C:v[0-9]+]]
-
-; GCN-SAFE: v_fma_f32 [[FMA:v[0-9]+]], -[[A]], [[B]], -[[C]]
-; GCN-SAFE: v_xor_b32_e32 v{{[[0-9]+}}, 0x80000000, [[FMA]]
-
-; GCN-NSZ: v_fma_f32 [[FMA:v[0-9]+]], [[A]], [[B]], [[C]]
-; GCN-NSZ-NOT: [[FMA]]
-; GCN-NSZ: flat_store_dword v{{\[[0-9]+:[0-9]+\]}}, [[FMA]]
+; GCN: v_fma_f32 [[FMA:v[0-9]+]], [[A]], [[B]], [[C]]
+; GCN-NOT: [[FMA]]
+; GCN: flat_store_dword v{{\[[0-9]+:[0-9]+\]}}, [[FMA]]
 define amdgpu_kernel void @v_fneg_fma_fneg_x_fneg_f32(float addrspace(1)* %out, float addrspace(1)* %a.ptr, float addrspace(1)* %b.ptr, float addrspace(1)* %c.ptr) #0 {
   %tid = call i32 @llvm.amdgcn.workitem.id.x()
   %tid.ext = sext i32 %tid to i64
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -848,7 +848,20 @@
 
     return isNegatibleForFree(Op.getOperand(1), LegalOperations, TLI, Options,
                               ForCodeSize, Depth + 1);
-
+  case ISD::FMA:
+  case ISD::FMAD: {
+    // fold (fneg (fma X, Y, Z)) -> (fma (fneg X), Y, (fneg Z))
+    // fold (fneg (fma X, Y, Z)) -> (fma X, (fneg Y), (fneg Z))
+    char V2 = isNegatibleForFree(Op.getOperand(2), LegalOperations, TLI,
+                                 Options, ForCodeSize, Depth + 1);
+    if (!V2)
+      return 0;
+    char V0 = isNegatibleForFree(Op.getOperand(0), LegalOperations, TLI,
+                                 Options, ForCodeSize, Depth + 1);
+    char V1 = isNegatibleForFree(Op.getOperand(1), LegalOperations, TLI,
+                                 Options, ForCodeSize, Depth + 1);
+    return std::max(std::max(V0, V1), V2);
+  }
   case ISD::FP_EXTEND:
   case ISD::FP_ROUND:
   case ISD::FSIN:
@@ -937,6 +950,32 @@
                                             LegalOperations, ForCodeSize,
                                             Depth + 1), Flags);
 
+  case ISD::FMA:
+  case ISD::FMAD: {
+    char V0 = isNegatibleForFree(Op.getOperand(0), LegalOperations,
+                                 DAG.getTargetLoweringInfo(), &Options,
+                                 ForCodeSize, Depth + 1);
+    char V1 = isNegatibleForFree(Op.getOperand(1), LegalOperations,
+                                 DAG.getTargetLoweringInfo(), &Options,
+                                 ForCodeSize, Depth + 1);
+    SDValue Neg2 = GetNegatedExpression(Op.getOperand(2), DAG, LegalOperations,
+                                        ForCodeSize, Depth + 1);
+
+    // fold (fneg (fma X, Y, Z)) -> (fma X, (fneg Y), (fneg Z))
+    if (V1 > V0) {
+      SDValue Neg1 = GetNegatedExpression(
+          Op.getOperand(1), DAG, LegalOperations, ForCodeSize, Depth + 1);
+      return DAG.getNode(Op.getOpcode(), SDLoc(Op), Op.getValueType(),
+                         Op.getOperand(0), Neg1, Neg2, Flags);
+    }
+
+    // fold (fneg (fma X, Y, Z)) -> (fma (fneg X), Y, (fneg Z))
+    SDValue Neg0 = GetNegatedExpression(Op.getOperand(0), DAG, LegalOperations,
+                                        ForCodeSize, Depth + 1);
+    return DAG.getNode(Op.getOpcode(), SDLoc(Op), Op.getValueType(), Neg0,
+                       Op.getOperand(1), Neg2, Flags);
+  }
+
   case ISD::FP_EXTEND:
   case ISD::FSIN:
     return DAG.getNode(Op.getOpcode(), SDLoc(Op), Op.getValueType(),


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