Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1637,6 +1637,20 @@
 
     break;
   }
+  case Intrinsic::cos:
+  case Intrinsic::amdgcn_cos: {
+    Value *SrcSrc;
+    Value *Src = II->getArgOperand(0);
+    if (match(Src, m_FNeg(m_Value(SrcSrc))) ||
+        match(Src, m_Intrinsic<Intrinsic::fabs>(m_Value(SrcSrc)))) {
+      // cos(-x) -> cos(x)
+      // cos(fabs(x)) -> cos(x)
+      II->setArgOperand(0, SrcSrc);
+      return II;
+    }
+
+    break;
+  }
   case Intrinsic::ppc_altivec_lvx:
   case Intrinsic::ppc_altivec_lvxl:
     // Turn PPC lvx -> load if the pointer is known aligned.
Index: test/Transforms/InstCombine/amdgcn-intrinsics.ll
===================================================================
--- test/Transforms/InstCombine/amdgcn-intrinsics.ll
+++ test/Transforms/InstCombine/amdgcn-intrinsics.ll
@@ -599,3 +599,37 @@
   %val = call i1 @llvm.amdgcn.class.f64(double 0x7FF0000000000001, i32 512)
   ret i1 %val
 }
+
+; --------------------------------------------------------------------
+; llvm.amdgcn.cos
+; --------------------------------------------------------------------
+declare float @llvm.amdgcn.cos.f32(float) nounwind readnone
+declare float @llvm.fabs.f32(float) nounwind readnone
+
+; CHECK-LABEL: @cos_fneg_f32(
+; CHECK: %cos = call float @llvm.amdgcn.cos.f32(float %x)
+; CHECK-NEXT: ret float %cos
+define float @cos_fneg_f32(float %x) {
+  %x.fneg = fsub float -0.0, %x
+  %cos = call float @llvm.amdgcn.cos.f32(float %x.fneg)
+  ret float %cos
+}
+
+; CHECK-LABEL: @cos_fabs_f32(
+; CHECK-NEXT: %cos = call float @llvm.amdgcn.cos.f32(float %x)
+; CHECK-NEXT: ret float %cos
+define float @cos_fabs_f32(float %x) {
+  %x.fabs = call float @llvm.fabs.f32(float %x)
+  %cos = call float @llvm.amdgcn.cos.f32(float %x.fabs)
+  ret float %cos
+}
+
+; CHECK-LABEL: @cos_fabs_fneg_f32(
+; CHECK-NEXT: %cos = call float @llvm.amdgcn.cos.f32(float %x)
+; CHECK-NEXT: ret float %cos
+define float @cos_fabs_fneg_f32(float %x) {
+  %x.fabs = call float @llvm.fabs.f32(float %x)
+  %x.fabs.fneg = fsub float -0.0, %x.fabs
+  %cos = call float @llvm.amdgcn.cos.f32(float %x.fabs.fneg)
+  ret float %cos
+}
Index: test/Transforms/InstCombine/cos-intrinsic.ll
===================================================================
--- test/Transforms/InstCombine/cos-intrinsic.ll
+++ test/Transforms/InstCombine/cos-intrinsic.ll
@@ -3,6 +3,10 @@
 
 declare double    @llvm.cos.f64(double %Val)
 declare float     @llvm.cos.f32(float %Val)
+declare <2 x float> @llvm.cos.v2f32(<2 x float> %Val)
+
+declare float @llvm.fabs.f32(float %Val)
+declare <2 x float> @llvm.fabs.v2f32(<2 x float> %Val)
 
 ; Function Attrs: nounwind readnone
 define double @test1() {
@@ -24,3 +28,54 @@
 ; CHECK-NEXT: %fsum
 ; CHECK: ret float %fsum
 }
+
+; CHECK-LABEL: @cos_fneg_f32(
+; CHECK: %cos = call float @llvm.cos.f32(float %x)
+; CHECK-NEXT: ret float %cos
+define float @cos_fneg_f32(float %x) {
+  %x.fneg = fsub float -0.0, %x
+  %cos = call float @llvm.cos.f32(float %x.fneg)
+  ret float %cos
+}
+
+; FIXME: m_FNeg() doesn't handle vectors
+; CHECK-LABEL: @cos_fneg_v2f32(
+; CHECK: %x.fneg = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, %x
+; CHECK-NEXT: %cos = call <2 x float> @llvm.cos.v2f32(<2 x float> %x.fneg)
+; CHECK-NEXT: ret <2 x float> %cos
+define <2 x float> @cos_fneg_v2f32(<2 x float> %x) {
+  %x.fneg = fsub <2 x float> <float -0.0, float -0.0>, %x
+  %cos = call <2 x float> @llvm.cos.v2f32(<2 x float> %x.fneg)
+  ret <2 x float> %cos
+}
+
+; CHECK-LABEL: @cos_fabs_f32(
+; CHECK-NEXT: %cos = call float @llvm.cos.f32(float %x)
+; CHECK-NEXT: ret float %cos
+define float @cos_fabs_f32(float %x) {
+  %x.fabs = call float @llvm.fabs.f32(float %x)
+  %cos = call float @llvm.cos.f32(float %x.fabs)
+  ret float %cos
+}
+
+; CHECK-LABEL: @cos_fabs_fneg_f32(
+; CHECK: %cos = call float @llvm.cos.f32(float %x)
+; CHECK-NEXT: ret float %cos
+define float @cos_fabs_fneg_f32(float %x) {
+  %x.fabs = call float @llvm.fabs.f32(float %x)
+  %x.fabs.fneg = fsub float -0.0, %x.fabs
+  %cos = call float @llvm.cos.f32(float %x.fabs.fneg)
+  ret float %cos
+}
+
+; CHECK-LABEL: @cos_fabs_fneg_v2f32(
+; CHECK: %x.fabs = call <2 x float> @llvm.fabs.v2f32(<2 x float> %x)
+; CHECK-NEXT: %x.fabs.fneg = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, %x.fabs
+; CHECK-NEXT: %cos = call <2 x float> @llvm.cos.v2f32(<2 x float> %x.fabs.fneg)
+; CHECK-NEXT: ret <2 x float> %cos
+define <2 x float> @cos_fabs_fneg_v2f32(<2 x float> %x) {
+  %x.fabs = call <2 x float> @llvm.fabs.v2f32(<2 x float> %x)
+  %x.fabs.fneg = fsub <2 x float> <float -0.0, float -0.0>, %x.fabs
+  %cos = call <2 x float> @llvm.cos.v2f32(<2 x float> %x.fabs.fneg)
+  ret <2 x float> %cos
+}