guard fsqrt with fmf sub flags

Summary:
This change uses fmf subflags to guard optimizations as well as unsafe. These changes originated from D46483.
It contains only context for fsqrt.


Reviewers: spatel, hfinkel, arsenm

Reviewed By: spatel

Subscribers: hfinkel, wdng, andrew.w.kaylor, wristow, efriedma, nemanjai

Differential Revision: https://reviews.llvm.org/D47749

llvm-svn: 334113

1 files changed, 4 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 50953275d33..6d59f330048 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -10893,17 +10893,16 @@ SDValue DAGCombiner::visitFREM(SDNode *N) {
 }
 
 SDValue DAGCombiner::visitFSQRT(SDNode *N) {
-  if (!DAG.getTarget().Options.UnsafeFPMath)
+  SDNodeFlags Flags = N->getFlags();
+  if (!DAG.getTarget().Options.UnsafeFPMath && 
+      !Flags.hasApproximateFuncs())
     return SDValue();
 
   SDValue N0 = N->getOperand(0);
   if (TLI.isFsqrtCheap(N0, DAG))
     return SDValue();
 
-  // TODO: FSQRT nodes should have flags that propagate to the created nodes.
-  // For now, create a Flags object for use with reassociation math transforms.
-  SDNodeFlags Flags;
-  Flags.setAllowReassociation(true);
+  // FSQRT nodes have flags that propagate to the created nodes.
   return buildSqrtEstimate(N0, Flags);
 }