1 files changed, 20 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 81886941009..5ae47c93936 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -622,7 +622,8 @@ static char isNegatibleForFree(SDValue Op, bool LegalOperations,
                               Depth + 1);
   case ISD::FSUB:
     // We can't turn -(A-B) into B-A when we honor signed zeros.
-    if (!Options->UnsafeFPMath) return 0;
+    if (!Options->UnsafeFPMath && !Op.getNode()->getFlags()->hasNoSignedZeros())
+      return 0;
 
     // fold (fneg (fsub A, B)) -> (fsub B, A)
     return 1;
@@ -685,9 +686,6 @@ static SDValue GetNegatedExpression(SDValue Op, SelectionDAG &DAG,
                                             LegalOperations, Depth+1),
                        Op.getOperand(0), Flags);
   case ISD::FSUB:
-    // We can't turn -(A-B) into B-A when we honor signed zeros.
-    assert(Options.UnsafeFPMath);
-
     // fold (fneg (fsub 0, B)) -> B
     if (ConstantFPSDNode *N0CFP = dyn_cast<ConstantFPSDNode>(Op.getOperand(0)))
       if (N0CFP->isZero())
@@ -8462,17 +8460,20 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
     return DAG.getNode(ISD::FSUB, DL, VT, N1,
                        GetNegatedExpression(N0, DAG, LegalOperations), Flags);
 
+  // FIXME: Auto-upgrade the target/function-level option.
+  if (Options.UnsafeFPMath || N->getFlags()->hasNoSignedZeros()) {
+    // fold (fadd A, 0) -> A
+    if (ConstantFPSDNode *N1C = isConstOrConstSplatFP(N1))
+      if (N1C->isZero())
+        return N0;
+  }
+
   // If 'unsafe math' is enabled, fold lots of things.
   if (Options.UnsafeFPMath) {
     // No FP constant should be created after legalization as Instruction
     // Selection pass has a hard time dealing with FP constants.
     bool AllowNewConst = (Level < AfterLegalizeDAG);
 
-    // fold (fadd A, 0) -> A
-    if (ConstantFPSDNode *N1C = isConstOrConstSplatFP(N1))
-      if (N1C->isZero())
-        return N0;
-
     // fold (fadd (fadd x, c1), c2) -> (fadd x, (fadd c1, c2))
     if (N1CFP && N0.getOpcode() == ISD::FADD && N0.getNode()->hasOneUse() &&
         isConstantFPBuildVectorOrConstantFP(N0.getOperand(1)))
@@ -8599,19 +8600,22 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) {
     return DAG.getNode(ISD::FADD, DL, VT, N0,
                        GetNegatedExpression(N1, DAG, LegalOperations), Flags);
 
-  // If 'unsafe math' is enabled, fold lots of things.
-  if (Options.UnsafeFPMath) {
-    // (fsub A, 0) -> A
-    if (N1CFP && N1CFP->isZero())
-      return N0;
-
+  // FIXME: Auto-upgrade the target/function-level option.
+  if (Options.UnsafeFPMath || N->getFlags()->hasNoSignedZeros()) {
     // (fsub 0, B) -> -B
     if (N0CFP && N0CFP->isZero()) {
       if (isNegatibleForFree(N1, LegalOperations, TLI, &Options))
         return GetNegatedExpression(N1, DAG, LegalOperations);
       if (!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))
-        return DAG.getNode(ISD::FNEG, DL, VT, N1);
+        return DAG.getNode(ISD::FNEG, DL, VT, N1, Flags);
     }
+  }
+
+  // If 'unsafe math' is enabled, fold lots of things.
+  if (Options.UnsafeFPMath) {
+    // (fsub A, 0) -> A
+    if (N1CFP && N1CFP->isZero())
+      return N0;
 
     // (fsub x, x) -> 0.0
     if (N0 == N1)