[llvm] AMDGPU: Add baseline tests for gep flag handling (PR #110814)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-x86_64-debian-fast` running on `gribozavr4` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/56/builds/9463

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: CodeGen/AMDGPU/gep-flags-stack-offsets.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 3: /b/1/clang-x86_64-debian-fast/llvm.obj/bin/llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx803 < /b/1/clang-x86_64-debian-fast/llvm.src/llvm/test/CodeGen/AMDGPU/gep-flags-stack-offsets.ll | /b/1/clang-x86_64-debian-fast/llvm.obj/bin/FileCheck -check-prefix=GFX8 /b/1/clang-x86_64-debian-fast/llvm.src/llvm/test/CodeGen/AMDGPU/gep-flags-stack-offsets.ll
+ /b/1/clang-x86_64-debian-fast/llvm.obj/bin/llc -mtriple=amdgcn-amd-amdhsa -mcpu=gfx803
+ /b/1/clang-x86_64-debian-fast/llvm.obj/bin/FileCheck -check-prefix=GFX8 /b/1/clang-x86_64-debian-fast/llvm.src/llvm/test/CodeGen/AMDGPU/gep-flags-stack-offsets.ll
/b/1/clang-x86_64-debian-fast/llvm.src/llvm/test/CodeGen/AMDGPU/gep-flags-stack-offsets.ll:12:14: error: GFX8-NEXT: expected string not found in input
; GFX8-NEXT: v_add_u32_e32 v0, vcc, v2, v0
             ^
<stdin>:11:30: note: scanning from here
 v_lshrrev_b32_e64 v2, 6, s32
                             ^
<stdin>:12:2: note: possible intended match here
 v_add_u32_e32 v0, vcc, v0, v2
 ^
/b/1/clang-x86_64-debian-fast/llvm.src/llvm/test/CodeGen/AMDGPU/gep-flags-stack-offsets.ll:39:14: error: GFX8-NEXT: expected string not found in input
; GFX8-NEXT: v_add_u32_e32 v0, vcc, v2, v0
             ^
<stdin>:44:30: note: scanning from here
 v_lshrrev_b32_e64 v2, 6, s32
                             ^
<stdin>:45:2: note: possible intended match here
 v_add_u32_e32 v0, vcc, v0, v2
 ^
/b/1/clang-x86_64-debian-fast/llvm.src/llvm/test/CodeGen/AMDGPU/gep-flags-stack-offsets.ll:66:14: error: GFX8-NEXT: expected string not found in input
; GFX8-NEXT: v_add_u32_e32 v0, vcc, v2, v0
             ^
<stdin>:77:30: note: scanning from here
 v_lshrrev_b32_e64 v2, 6, s32
                             ^
<stdin>:78:2: note: possible intended match here
 v_add_u32_e32 v0, vcc, v0, v2
 ^
/b/1/clang-x86_64-debian-fast/llvm.src/llvm/test/CodeGen/AMDGPU/gep-flags-stack-offsets.ll:93:14: error: GFX8-NEXT: expected string not found in input
; GFX8-NEXT: v_add_u32_e32 v0, vcc, v2, v0
             ^
<stdin>:110:30: note: scanning from here
 v_lshrrev_b32_e64 v2, 6, s32
                             ^
<stdin>:111:2: note: possible intended match here
 v_add_u32_e32 v0, vcc, v0, v2
 ^
/b/1/clang-x86_64-debian-fast/llvm.src/llvm/test/CodeGen/AMDGPU/gep-flags-stack-offsets.ll:120:14: error: GFX8-NEXT: expected string not found in input
; GFX8-NEXT: v_add_u32_e32 v0, vcc, v2, v0
             ^
<stdin>:143:30: note: scanning from here
 v_lshrrev_b32_e64 v2, 6, s32
                             ^
...

```

</details>

https://github.com/llvm/llvm-project/pull/110814