diff --git a/llvm/lib/Target/X86/X86FastISel.cpp b/llvm/lib/Target/X86/X86FastISel.cpp
--- a/llvm/lib/Target/X86/X86FastISel.cpp
+++ b/llvm/lib/Target/X86/X86FastISel.cpp
@@ -3842,6 +3842,31 @@
     return X86MaterializeFP(CFP, VT);
   else if (const GlobalValue *GV = dyn_cast<GlobalValue>(C))
     return X86MaterializeGV(GV, VT);
+  else if (isa<UndefValue>(C)) {
+    unsigned Opc = 0;
+    switch (VT.SimpleTy) {
+    default:
+      break;
+    case MVT::f32:
+      if (!X86ScalarSSEf32)
+        Opc = X86::LD_Fp032;
+      break;
+    case MVT::f64:
+      if (!X86ScalarSSEf64)
+        Opc = X86::LD_Fp064;
+      break;
+    case MVT::f80:
+      Opc = X86::LD_Fp080;
+      break;
+    }
+
+    if (Opc) {
+      Register ResultReg = createResultReg(TLI.getRegClassFor(VT));
+      BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(Opc),
+              ResultReg);
+      return ResultReg;
+    }
+  }
 
   return 0;
 }
diff --git a/llvm/test/CodeGen/X86/fast-isel-undef-fp.ll b/llvm/test/CodeGen/X86/fast-isel-undef-fp.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/CodeGen/X86/fast-isel-undef-fp.ll
@@ -0,0 +1,51 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc %s -o - -verify-machineinstrs -fast-isel=true -mattr=-sse | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define dso_local x86_fp80 @test_f80() {
+; CHECK-LABEL: test_f80:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    fldz
+; CHECK-NEXT:    fchs
+; CHECK-NEXT:    retq
+entry:
+  %fneg1 = fneg contract x86_fp80 undef
+  br label %exit
+
+exit:                                             ; preds = %entry
+  ret x86_fp80 %fneg1
+}
+
+define dso_local void @test_f32(float *%p) {
+; CHECK-LABEL: test_f32:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    fldz
+; CHECK-NEXT:    fchs
+; CHECK-NEXT:    fstps (%rdi)
+; CHECK-NEXT:    retq
+entry:
+  %fneg1 = fneg contract float undef
+  br label %exit
+
+exit:                                             ; preds = %entry
+  store float %fneg1, float *%p
+  ret void
+}
+
+define dso_local void @test_f64(double *%p) {
+; CHECK-LABEL: test_f64:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    fldz
+; CHECK-NEXT:    fchs
+; CHECK-NEXT:    fstpl (%rdi)
+; CHECK-NEXT:    retq
+entry:
+  %fneg1 = fneg contract double undef
+  br label %exit
+
+exit:                                             ; preds = %entry
+  store double %fneg1, double *%p
+  ret void
+}