Add a few more simple fast-math constant propagations and cancellations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167200 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 38 insertions, 0 deletions

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 23821e6f60..a83203b663 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5729,6 +5729,18 @@ SDValue DAGCombiner::visitFADD(SDNode *N) {
                        DAG.getNode(ISD::FADD, N->getDebugLoc(), VT,
                                    N0.getOperand(1), N1));
 
+  // If allow, fold (fadd (fneg x), x) -> 0.0
+  if (DAG.getTarget().Options.UnsafeFPMath &&
+      N0.getOpcode() == ISD::FNEG && N0.getOperand(0) == N1) {
+    return DAG.getConstantFP(0.0, VT);
+  }
+
+    // If allow, fold (fadd x, (fneg x)) -> 0.0
+  if (DAG.getTarget().Options.UnsafeFPMath &&
+      N1.getOpcode() == ISD::FNEG && N1.getOperand(0) == N0) {
+    return DAG.getConstantFP(0.0, VT);
+  }
+
   // In unsafe math mode, we can fold chains of FADD's of the same value
   // into multiplications.  This transform is not safe in general because
   // we are reducing the number of rounding steps.
@@ -6038,6 +6050,12 @@ SDValue DAGCombiner::visitFMA(SDNode *N) {
   EVT VT = N->getValueType(0);
   DebugLoc dl = N->getDebugLoc();
 
+  if (DAG.getTarget().Options.UnsafeFPMath) {
+    if (N0CFP && N0CFP->isZero())
+      return N2;
+    if (N1CFP && N1CFP->isZero())
+      return N2;
+  }
   if (N0CFP && N0CFP->isExactlyValue(1.0))
     return DAG.getNode(ISD::FADD, N->getDebugLoc(), VT, N1, N2);
   if (N1CFP && N1CFP->isExactlyValue(1.0))
diff --git a/test/CodeGen/X86/fp-fast.ll b/test/CodeGen/X86/fp-fast.ll
index 091f0de930..192a127358 100644
--- a/test/CodeGen/X86/fp-fast.ll
+++ b/test/CodeGen/X86/fp-fast.ll
@@ -35,3 +35,23 @@ define float @test3(float %a) {
   ret float %r
 }
 
+; CHECK: test4
+define float @test4(float %a) {
+; CHECK-NOT: fma
+; CHECK-NOT mul
+; CHECK-NOT: add
+; CHECK: ret
+  %t1 = fmul float %a, 0.0
+  %t2 = fadd float %a, %t1
+  ret float %t2
+}
+
+; CHECK: test5
+define float @test5(float %a) {
+; CHECK-NOT: add
+; CHECK: vxorps
+; CHECK: ret
+  %t1 = fsub float -0.0, %a
+  %t2 = fadd float %a, %t1
+  ret float %t2
+}