Use same subtarget. Test sub.

Signed-off-by: John Lu <[email protected]>

Author: LU-JOHN

llvm/test/CodeGen/AMDGPU/s_uaddo_pseudo.ll

@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
-; RUN: llc -mtriple=amdgcn-amd-amdpal -stop-after=amdgpu-isel < %s | FileCheck -check-prefixes=GCN-ISEL %s
+; RUN: llc -mtriple=amdgcn-amd-amdpal -mcpu=gfx900 -stop-after=amdgpu-isel < %s | FileCheck -check-prefixes=GCN-ISEL %s
 ; RUN: llc -mtriple=amdgcn-amd-amdpal -mcpu=gfx900 < %s | FileCheck %s
 ; Ensure that S_UADDO_PSEUDO is selected when carryout user is S_ADD_CO_PSEUDO
 
@@ -22,5 +22,25 @@ define amdgpu_ps i32 @s_uaddo_pseudo(i32 inreg %val0) {
   %result = add i32 %zext_carryout, 1
   ret i32 %result
 }
+
+; GCN-ISEL-LABEL: name:   s_usubo_pseudo
+; GCN-ISEL-LABEL: body:
+; GCN-ISEL: S_USUBO_PSEUDO
+; GCN-ISEL: S_SUB_CO_PSEUDO
+
+define amdgpu_ps i32 @s_usubo_pseudo(i32 inreg %val0, i32 inreg %val1) {
+; CHECK-LABEL: s_usubo_pseudo:
+; CHECK:       ; %bb.0:
+; CHECK-NEXT:    s_sub_u32 s0, s0, 1
+; CHECK-NEXT:    s_cselect_b64 s[2:3], -1, 0
+; CHECK-NEXT:    s_cmp_lg_u64 s[2:3], 0
+; CHECK-NEXT:    s_subb_u32 s0, s1, 0
+; CHECK-NEXT:    ; return to shader part epilog
+  %pair = call { i32, i1 } @llvm.usub.with.overflow.i32(i32 %val0, i32 1)
+  %carryout = extractvalue { i32, i1 } %pair, 1
+  %zext_carryout = zext i1 %carryout to i32
+  %result = sub i32 %val1, %zext_carryout
+  ret i32 %result
+}
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 ; GCN-ISEL: {{.*}}