Index: lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4442,7 +4442,7 @@
   case ISD::FMUL:
   case ISD::FDIV:
   case ISD::FREM:
-    if (getTarget().Options.UnsafeFPMath) {
+    if (getTarget().Options.UnsafeFPMath || Flags.isFast()) {
       if (Opcode == ISD::FADD) {
         // x+0 --> x
         if (N2CFP && N2CFP->getValueAPF().isZero())
Index: lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2769,6 +2769,10 @@
     Flags.setVectorReduction(true);
     LLVM_DEBUG(dbgs() << "Detected a reduction operation:" << I << "\n");
   }
+  // need Flags for Selection DAG decisions here
+  if (auto *FPMO = dyn_cast<FPMathOperator>(&I)) {
+    Flags.copyFMF(*FPMO);
+  }
 
   SDValue Op1 = getValue(I.getOperand(0));
   SDValue Op2 = getValue(I.getOperand(1));
Index: test/CodeGen/X86/fp-fold.ll
===================================================================
--- test/CodeGen/X86/fp-fold.ll
+++ test/CodeGen/X86/fp-fold.ll
@@ -0,0 +1,39 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown                        | FileCheck %s 
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -enable-unsafe-fp-math | FileCheck %s 
+
+; This is duplicated from tests for InstSimplify. If you're
+; adding something here, you should probably add it there too.
+
+define float @fadd_zero(float %x) {
+; CHECK-LABEL: fadd_zero:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    retq
+  %r = fadd fast float %x, 0.0
+  ret float %r
+}
+
+define float @fsub_zero(float %x) {
+; CHECK-LABEL: fsub_zero:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    retq
+  %r = fsub fast float %x, 0.0
+  ret float %r
+}
+
+define float @fmul_zero(float %x) {
+; CHECK-LABEL: fmul_zero:
+; CHECK:       # %bb.0:
+; CHECK:         xorps	%xmm0, %xmm0
+; CHECK-NEXT:    retq
+  %r = fmul fast float %x, 0.0
+  ret float %r
+}
+
+define float @fmul_one(float %x) {
+; CHECK-LABEL: fmul_one:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    retq
+  %r = fmul fast float %x, 1.0
+  ret float %r
+}