Don't do the X * 0.0 -> 0.0 transformation in instcombine, because

instcombine doesn't know when it's safe. To partially compensate
for this, introduce new code to do this transformation in
dagcombine, which can use UnsafeFPMath.

llvm-svn: 72872

2 files changed, 11 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4c1710dd81f..5d1b2a3ea28 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4019,6 +4019,9 @@ SDValue DAGCombiner::visitFMUL(SDNode *N) {
   // fold (fmul A, 0) -> 0
   if (UnsafeFPMath && N1CFP && N1CFP->getValueAPF().isZero())
     return N1;
+  // fold (fmul A, 0) -> 0, vector edition.
+  if (UnsafeFPMath && ISD::isBuildVectorAllZeros(N1.getNode()))
+    return N1;
   // fold (fmul X, 2.0) -> (fadd X, X)
   if (N1CFP && N1CFP->isExactlyValue(+2.0))
     return DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N0, N0);
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 2c645e42083..c2c884e8d17 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2807,16 +2807,19 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL, MVT VT,
     case ISD::ADDC:
     case ISD::ADDE:
     case ISD::SUB:
-    case ISD::FADD:
-    case ISD::FSUB:
-    case ISD::FMUL:
-    case ISD::FDIV:
-    case ISD::FREM:
     case ISD::UDIV:
     case ISD::SDIV:
     case ISD::UREM:
     case ISD::SREM:
       return N2;       // fold op(arg1, undef) -> undef
+    case ISD::FADD:
+    case ISD::FSUB:
+    case ISD::FMUL:
+    case ISD::FDIV:
+    case ISD::FREM:
+      if (UnsafeFPMath)
+        return N2;
+      break;
     case ISD::MUL:
     case ISD::AND:
     case ISD::SRL: