[SelectionDAG] Allow sin/cos -> sincos optimization on GNU triples w/ just -fno-math-errno

Summary:
This change enables the sin(x) cos(x) -> sincos(x) optimization on GNU
target triples.  This optimization was being inhibited when -ffast-math
wasn't set because sincos in GLibC does not set errno, while sin and cos
do.  However, this optimization will only run if the attributes on the
sin/cos calls include readnone, which is how clang represents the fact
that it doesn't care about the errno values set by these functions (via
the -fno-math-errno flag).

Reviewers: hfinkel, bogner

Subscribers: mcrosier, javed.absar, llvm-commits, paul.redmond

Differential Revision: https://reviews.llvm.org/D32921

llvm-svn: 305204

1 files changed, 1 insertions, 14 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index e54eaa3b81b..15e87b7af18 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -2192,19 +2192,6 @@ static bool isSinCosLibcallAvailable(SDNode *Node, const TargetLowering &TLI) {
   return TLI.getLibcallName(LC) != nullptr;
 }
 
-/// Return true if sincos libcall is available and can be used to combine sin
-/// and cos.
-static bool canCombineSinCosLibcall(SDNode *Node, const TargetLowering &TLI,
-                                    const TargetMachine &TM) {
-  if (!isSinCosLibcallAvailable(Node, TLI))
-    return false;
-  // GNU sin/cos functions set errno while sincos does not. Therefore
-  // combining sin and cos is only safe if unsafe-fpmath is enabled.
-  if (TM.getTargetTriple().isGNUEnvironment() && !TM.Options.UnsafeFPMath)
-    return false;
-  return true;
-}
-
 /// Only issue sincos libcall if both sin and cos are needed.
 static bool useSinCos(SDNode *Node) {
   unsigned OtherOpcode = Node->getOpcode() == ISD::FSIN
@@ -3247,7 +3234,7 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     // Turn fsin / fcos into ISD::FSINCOS node if there are a pair of fsin /
     // fcos which share the same operand and both are used.
     if ((TLI.isOperationLegalOrCustom(ISD::FSINCOS, VT) ||
-         canCombineSinCosLibcall(Node, TLI, TM))
+         isSinCosLibcallAvailable(Node, TLI))
         && useSinCos(Node)) {
       SDVTList VTs = DAG.getVTList(VT, VT);
       Tmp1 = DAG.getNode(ISD::FSINCOS, dl, VTs, Node->getOperand(0));