[DAGCombiner] Expand combining of FP logical ops to sign-setting FP ops

We already do the following combines:
(bitcast int (and (bitcast fp X to int), 0x7fff...) to fp) -> fabs X
(bitcast int (xor (bitcast fp X to int), 0x8000...) to fp) -> fneg X

When the target has "bit preserving fp logic". This patch just extends it
to also combine:
(bitcast int (or (bitcast fp X to int), 0x8000...) to fp) -> fneg (fabs X)

As some targets have fnabs and even those that don't can efficiently lower
both the fabs and the fneg.

Differential revision: https://reviews.llvm.org/D44548

llvm-svn: 344093

1 files changed, 14 insertions, 3 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 9c70b662c86..29adcad22e1 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -83,6 +83,7 @@ STATISTIC(PostIndexedNodes, "Number of post-indexed nodes created");
 STATISTIC(OpsNarrowed     , "Number of load/op/store narrowed");
 STATISTIC(LdStFP2Int      , "Number of fp load/store pairs transformed to int");
 STATISTIC(SlicedLoads, "Number of load sliced");
+STATISTIC(NumFPLogicOpsConv, "Number of logic ops converted to fp ops");
 
 static cl::opt<bool>
 CombinerGlobalAA("combiner-global-alias-analysis", cl::Hidden,
@@ -9843,19 +9844,29 @@ static SDValue foldBitcastedFPLogic(SDNode *N, SelectionDAG &DAG,
     FPOpcode = ISD::FNEG;
     SignMask = APInt::getSignMask(SourceVT.getScalarSizeInBits());
     break;
-  // TODO: ISD::OR --> ISD::FNABS?
+  case ISD::OR:
+    FPOpcode = ISD::FABS;
+    SignMask = APInt::getSignMask(SourceVT.getScalarSizeInBits());
+    break;
   default:
     return SDValue();
   }
 
   // Fold (bitcast int (and (bitcast fp X to int), 0x7fff...) to fp) -> fabs X
   // Fold (bitcast int (xor (bitcast fp X to int), 0x8000...) to fp) -> fneg X
+  // Fold (bitcast int (or (bitcast fp X to int), 0x8000...) to fp) ->
+  //   fneg (fabs X)
   SDValue LogicOp0 = N0.getOperand(0);
   ConstantSDNode *LogicOp1 = isConstOrConstSplat(N0.getOperand(1), true);
   if (LogicOp1 && LogicOp1->getAPIntValue() == SignMask &&
       LogicOp0.getOpcode() == ISD::BITCAST &&
-      LogicOp0.getOperand(0).getValueType() == VT)
-    return DAG.getNode(FPOpcode, SDLoc(N), VT, LogicOp0.getOperand(0));
+      LogicOp0.getOperand(0).getValueType() == VT) {
+    SDValue FPOp = DAG.getNode(FPOpcode, SDLoc(N), VT, LogicOp0.getOperand(0));
+    NumFPLogicOpsConv++;
+    if (N0.getOpcode() == ISD::OR)
+      return DAG.getNode(ISD::FNEG, SDLoc(N), VT, FPOp);
+    return FPOp;
+  }
 
   return SDValue();
 }