--- a/test/CodeGen/X86/vec_fneg.ll	Thu Dec 12 15:22:36 2013 +0900
+++ b/test/CodeGen/X86/vec_fneg.ll	Mon Sep 08 22:06:00 2014 +0900
@@ -1,11 +1,45 @@
-; RUN: llc < %s -march=x86 -mattr=+sse2
+; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mcpu=corei7 | FileCheck %s
 
+; FNEG is defined as subtraction from -0.0.
+
+; This test verifies that we use an xor with a constant to flip the sign bits; no subtraction needed.
 define <4 x float> @t1(<4 x float> %Q) {
-        %tmp15 = fsub <4 x float> < float -0.000000e+00, float -0.000000e+00, float -0.000000e+00, float -0.000000e+00 >, %Q
-	ret <4 x float> %tmp15
+; CHECK-LABEL: t1:
+; CHECK: xorps	{{.*}}LCPI0_0{{.*}}, %xmm0
+; CHECK-NEXT: retq
+        %tmp = fsub <4 x float> < float -0.000000e+00, float -0.000000e+00, float -0.000000e+00, float -0.000000e+00 >, %Q
+	ret <4 x float> %tmp
 }
 
+; This test verifies that we generate an FP subtraction because "0.0 - x" is not an fneg.
 define <4 x float> @t2(<4 x float> %Q) {
-        %tmp15 = fsub <4 x float> zeroinitializer, %Q
-	ret <4 x float> %tmp15
+; CHECK-LABEL: t2:
+; CHECK: xorps	%[[X:xmm[0-9]+]], %[[X]]
+; CHECK-NEXT: subps	%xmm0, %[[X]]
+; CHECK-NEXT: movaps	%[[X]], %xmm0
+; CHECK-NEXT: retq
+        %tmp = fsub <4 x float> zeroinitializer, %Q
+	ret <4 x float> %tmp
 }
+
+; If we're bitcasting an integer to an FP vector, we should avoid the FPU/vector unit entirely.
+; Make sure that we're flipping the sign bit and only the sign bit of each float.
+; So instead of something like this:
+;    movd	%rdi, %xmm0
+;    xorps	.LCPI2_0(%rip), %xmm0
+;
+; We should generate:
+;    movabsq     (put sign bit mask in integer register))
+;    xorq        (flip sign bits)
+;    movd        (move to xmm return register) 
+
+define <2 x float> @fneg_bitcast(i64 %i) {
+; CHECK-LABEL: fneg_bitcast:
+; CHECK:	movabsq	$-9223372034707292160, %rax # imm = 0x8000000080000000
+; CHECK-NEXT:	xorq	%rdi, %rax
+; CHECK-NEXT:	movd	%rax, %xmm0
+; CHECK-NEXT:	retq
+  %bitcast = bitcast i64 %i to <2 x float>
+  %fneg = fsub <2 x float> <float -0.0, float -0.0>, %bitcast
+  ret <2 x float> %fneg
+}