Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -3426,6 +3426,24 @@
     Value *Src1 = II->getArgOperand(1);
     Value *Src2 = II->getArgOperand(2);
 
+    // Checking for NaN before canonicalization provides better fidelity when
+    // mapping other operations onto fmed3 since the order of operands is
+    // unchanged.
+    CallInst *NewCall = nullptr;
+    if (match(Src0, m_NaN()) || isa<UndefValue>(Src0)) {
+      NewCall = Builder.CreateMinNum(Src1, Src2);
+    } else if (match(Src1, m_NaN()) || isa<UndefValue>(Src1)) {
+      NewCall = Builder.CreateMinNum(Src0, Src2);
+    } else if (match(Src2, m_NaN()) || isa<UndefValue>(Src2)) {
+      NewCall = Builder.CreateMaxNum(Src0, Src1);
+    }
+
+    if (NewCall) {
+      NewCall->copyFastMathFlags(II);
+      NewCall->takeName(II);
+      return replaceInstUsesWith(*II, NewCall);
+    }
+
     bool Swap = false;
     // Canonicalize constants to RHS operands.
     //
@@ -3452,13 +3470,6 @@
       return II;
     }
 
-    if (match(Src2, m_NaN()) || isa<UndefValue>(Src2)) {
-      CallInst *NewCall = Builder.CreateMinNum(Src0, Src1);
-      NewCall->copyFastMathFlags(II);
-      NewCall->takeName(II);
-      return replaceInstUsesWith(*II, NewCall);
-    }
-
     if (const ConstantFP *C0 = dyn_cast<ConstantFP>(Src0)) {
       if (const ConstantFP *C1 = dyn_cast<ConstantFP>(Src1)) {
         if (const ConstantFP *C2 = dyn_cast<ConstantFP>(Src2)) {
Index: test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
===================================================================
--- test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
+++ test/Transforms/InstCombine/AMDGPU/amdgcn-intrinsics.ll
@@ -1229,7 +1229,7 @@
 }
 
 ; CHECK-LABEL: @fmed3_x_y_undef_f32(
-; CHECK: call float @llvm.minnum.f32(float %x, float %y)
+; CHECK: call float @llvm.maxnum.f32(float %x, float %y)
 define float @fmed3_x_y_undef_f32(float %x, float %y) {
   %med3 = call float @llvm.amdgcn.fmed3.f32(float %x, float %y, float undef)
   ret float %med3
@@ -1250,7 +1250,7 @@
 }
 
 ; CHECK-LABEL: @fmed3_x_y_qnan0_f32(
-; CHECK: call float @llvm.minnum.f32(float %x, float %y)
+; CHECK: call float @llvm.maxnum.f32(float %x, float %y)
 define float @fmed3_x_y_qnan0_f32(float %x, float %y) {
   %med3 = call float @llvm.amdgcn.fmed3.f32(float %x, float %y, float 0x7FF8000000000000)
   ret float %med3
@@ -1265,7 +1265,7 @@
 
 ; This can return any of the qnans.
 ; CHECK-LABEL: @fmed3_qnan0_qnan1_qnan2_f32(
-; CHECK: ret float 0x7FF8002000000000
+; CHECK: ret float 0x7FF8030000000000
 define float @fmed3_qnan0_qnan1_qnan2_f32(float %x, float %y) {
   %med3 = call float @llvm.amdgcn.fmed3.f32(float 0x7FF8000100000000, float 0x7FF8002000000000, float 0x7FF8030000000000)
   ret float %med3
@@ -1334,6 +1334,48 @@
   ret float %med3
 }
 
+; CHECK-LABEL: @fmed3_nan_0_1_f32(
+; CHECK: ret float 0.0
+define float @fmed3_nan_0_1_f32() {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float 0x7FF8001000000000, float 0.0, float 1.0)
+  ret float %med3
+}
+
+; CHECK-LABEL: @fmed3_0_nan_1_f32(
+; CHECK: ret float 0.0
+define float @fmed3_0_nan_1_f32() {
+  %med = call float @llvm.amdgcn.fmed3.f32(float 0.0, float 0x7FF8001000000000, float 1.0)
+  ret float %med
+}
+
+; CHECK-LABEL: @fmed3_0_1_nan_f32(
+; CHECK: ret float 1.0
+define float @fmed3_0_1_nan_f32() {
+  %med = call float @llvm.amdgcn.fmed3.f32(float 0.0, float 1.0, float 0x7FF8001000000000)
+  ret float %med
+}
+
+; CHECK-LABEL: @fmed3_undef_0_1_f32(
+; CHECK: ret float 0.0
+define float @fmed3_undef_0_1_f32() {
+  %med3 = call float @llvm.amdgcn.fmed3.f32(float undef, float 0.0, float 1.0)
+  ret float %med3
+}
+
+; CHECK-LABEL: @fmed3_0_undef_1_f32(
+; CHECK: ret float 0.0
+define float @fmed3_0_undef_1_f32() {
+  %med = call float @llvm.amdgcn.fmed3.f32(float 0.0, float undef, float 1.0)
+  ret float %med
+}
+
+; CHECK-LABEL: @fmed3_0_1_undef_f32(
+; CHECK: ret float 1.0
+define float @fmed3_0_1_undef_f32() {
+  %med = call float @llvm.amdgcn.fmed3.f32(float 0.0, float 1.0, float undef)
+  ret float %med
+}
+
 ; --------------------------------------------------------------------
 ; llvm.amdgcn.icmp
 ; --------------------------------------------------------------------