Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1846,6 +1846,20 @@
 
     break;
   }
+  case Intrinsic::amdgcn_frexp_mant: {
+    Value *Src = II->getArgOperand(0);
+    if (const ConstantFP *C = dyn_cast<ConstantFP>(Src)) {
+      int Exp;
+      APFloat Significand = frexp(C->getValueAPF(), Exp,
+                                  APFloat::rmNearestTiesToEven);
+
+      return replaceInstUsesWith(CI, ConstantFP::get(II->getContext(),
+                                                     Significand));
+    } else if (isa<UndefValue>(Src))
+      return replaceInstUsesWith(CI, Src);
+
+    break;
+  }
   case Intrinsic::stackrestore: {
     // If the save is right next to the restore, remove the restore.  This can
     // happen when variable allocas are DCE'd.
Index: test/Transforms/InstCombine/amdgcn-intrinsics.ll
===================================================================
--- test/Transforms/InstCombine/amdgcn-intrinsics.ll
+++ test/Transforms/InstCombine/amdgcn-intrinsics.ll
@@ -1,8 +1,13 @@
 ; RUN: opt -instcombine -S < %s | FileCheck %s
 
+; --------------------------------------------------------------------
+; llvm.amdgcn.rcp
+; --------------------------------------------------------------------
+
 declare float @llvm.amdgcn.rcp.f32(float) nounwind readnone
 declare double @llvm.amdgcn.rcp.f64(double) nounwind readnone
 
+
 ; CHECK-LABEL: @test_constant_fold_rcp_f32_1
 ; CHECK-NEXT: ret float 1.000000e+00
 define float @test_constant_fold_rcp_f32_1() nounwind {
@@ -45,3 +50,153 @@
   ret double %val
 }
 
+
+; --------------------------------------------------------------------
+; llvm.amdgcn.frexp.mant
+; --------------------------------------------------------------------
+
+declare float @llvm.amdgcn.frexp.mant.f32(float) nounwind readnone
+declare double @llvm.amdgcn.frexp.mant.f64(double) nounwind readnone
+
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_undef(
+; CHECK-NEXT: ret float undef
+define float @test_constant_fold_frexp_mant_f32_undef() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float undef)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_undef(
+; CHECK-NEXT:  ret double undef
+define double @test_constant_fold_frexp_mant_f64_undef() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double undef)
+  ret double %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_0(
+; CHECK-NEXT: ret float 0.000000e+00
+define float @test_constant_fold_frexp_mant_f32_0() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float 0.0)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_0(
+; CHECK-NEXT:  ret double 0.000000e+00
+define double @test_constant_fold_frexp_mant_f64_0() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double 0.0)
+  ret double %val
+}
+
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_n0(
+; CHECK-NEXT: ret float -0.000000e+00
+define float @test_constant_fold_frexp_mant_f32_n0() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float -0.0)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_n0(
+; CHECK-NEXT:  ret double -0.000000e+00
+define double @test_constant_fold_frexp_mant_f64_n0() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double -0.0)
+  ret double %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_1(
+; CHECK-NEXT: ret float 5.000000e-01
+define float @test_constant_fold_frexp_mant_f32_1() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float 1.0)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_1(
+; CHECK-NEXT:  ret double 5.000000e-01
+define double @test_constant_fold_frexp_mant_f64_1() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double 1.0)
+  ret double %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_n1(
+; CHECK-NEXT: ret float -5.000000e-01
+define float @test_constant_fold_frexp_mant_f32_n1() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float -1.0)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_n1(
+; CHECK-NEXT:  ret double -5.000000e-01
+define double @test_constant_fold_frexp_mant_f64_n1() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double -1.0)
+  ret double %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_nan(
+; CHECK-NEXT: ret float 0x7FF8000000000000
+define float @test_constant_fold_frexp_mant_f32_nan() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float 0x7FF8000000000000)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_nan(
+; CHECK-NEXT:  ret double 0x7FF8000000000000
+define double @test_constant_fold_frexp_mant_f64_nan() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double 0x7FF8000000000000)
+  ret double %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_inf(
+; CHECK-NEXT: ret float 0x7FF0000000000000
+define float @test_constant_fold_frexp_mant_f32_inf() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float 0x7FF0000000000000)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_inf(
+; CHECK-NEXT:  ret double 0x7FF0000000000000
+define double @test_constant_fold_frexp_mant_f64_inf() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double 0x7FF0000000000000)
+  ret double %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_ninf(
+; CHECK-NEXT: ret float 0xFFF0000000000000
+define float @test_constant_fold_frexp_mant_f32_ninf() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float 0xFFF0000000000000)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_ninf(
+; CHECK-NEXT:  ret double 0xFFF0000000000000
+define double @test_constant_fold_frexp_mant_f64_ninf() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double 0xFFF0000000000000)
+  ret double %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_max_num(
+; CHECK-NEXT: ret float 0x3FEFFFFFE0000000
+define float @test_constant_fold_frexp_mant_f32_max_num() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float 0x47EFFFFFE0000000)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_max_num(
+; CHECK-NEXT:  ret double 0x3FEFFFFFFFFFFFFF
+define double @test_constant_fold_frexp_mant_f64_max_num() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double 0x7FEFFFFFFFFFFFFF)
+  ret double %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f32_min_num(
+; CHECK-NEXT: ret float 5.000000e-01
+define float @test_constant_fold_frexp_mant_f32_min_num() nounwind {
+  %val = call float @llvm.amdgcn.frexp.mant.f32(float 0x36A0000000000000)
+  ret float %val
+}
+
+; CHECK-LABEL: @test_constant_fold_frexp_mant_f64_min_num(
+; CHECK-NEXT:  ret double 5.000000e-01
+define double @test_constant_fold_frexp_mant_f64_min_num() nounwind {
+  %val = call double @llvm.amdgcn.frexp.mant.f64(double 4.940656e-324)
+  ret double %val
+}
+