[llvm] [AMDGPU] Expand scratch atomics to flat atomics if GAS is enabled (PR #154710)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `profcheck` running on `profcheck-b2` while building `llvm` at step 5 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/223/builds/22

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

```
Step 5 (annotate) failure: '../llvm-zorg/zorg/buildbot/builders/annotated/profcheck.sh --jobs=64' (failure)
...
UNSUPPORTED: LLVM :: MC/Disassembler/M68k/atomics.txt (60201 of 60211)
UNSUPPORTED: LLVM :: MC/Disassembler/M68k/shift-rotate.txt (60202 of 60211)
UNSUPPORTED: LLVM :: MC/M68k/Arith/Classes/MxFBinary_FF.s (60203 of 60211)
UNSUPPORTED: LLVM :: MC/M68k/Bits/Classes/MxBTST_RI.s (60204 of 60211)
UNSUPPORTED: LLVM :: Other/ChangePrinters/DotCfg/print-changed-dot-cfg.mir (60205 of 60211)
UNSUPPORTED: LLVM :: tools/gold/X86/devirt_vcall_vis_export_dynamic.ll (60206 of 60211)
UNSUPPORTED: LLVM :: tools/gold/X86/time-trace.ll (60207 of 60211)
UNSUPPORTED: LLVM :: CodeGen/M68k/CollapseMOVEM.mir (60208 of 60211)
UNSUPPORTED: LLVM :: CodeGen/M68k/multiple-return.ll (60209 of 60211)
UNSUPPORTED: LLVM :: MC/M68k/Relocations/tls.s (60210 of 60211)
FAIL: LLVM :: Transforms/AtomicExpand/AMDGPU/expand-atomic-private-gas.ll (60211 of 60211)
********************
Failed Tests (1):
  LLVM :: Transforms/AtomicExpand/AMDGPU/expand-atomic-private-gas.ll


Testing Time: 169.79s

Total Discovered Tests: 68777
  Excluded   :  2170 (3.16%)
  Skipped    :    16 (0.02%)
  Unsupported:  1038 (1.51%)
  Passed     : 65552 (95.31%)
  Failed     :     1 (0.00%)
FAILED: test/CMakeFiles/check-llvm /b/profcheck-build/build/test/CMakeFiles/check-llvm 
cd /b/profcheck-build/build/test && /usr/bin/python3 /b/profcheck-build/build/./bin/llvm-lit --exclude-xfail /b/profcheck-build/build/test
ninja: build stopped: subcommand failed.
Step 7 (Ninja) failure: Ninja (failure)
...
UNSUPPORTED: LLVM :: MC/Disassembler/M68k/atomics.txt (60201 of 60211)
UNSUPPORTED: LLVM :: MC/Disassembler/M68k/shift-rotate.txt (60202 of 60211)
UNSUPPORTED: LLVM :: MC/M68k/Arith/Classes/MxFBinary_FF.s (60203 of 60211)
UNSUPPORTED: LLVM :: MC/M68k/Bits/Classes/MxBTST_RI.s (60204 of 60211)
UNSUPPORTED: LLVM :: Other/ChangePrinters/DotCfg/print-changed-dot-cfg.mir (60205 of 60211)
UNSUPPORTED: LLVM :: tools/gold/X86/devirt_vcall_vis_export_dynamic.ll (60206 of 60211)
UNSUPPORTED: LLVM :: tools/gold/X86/time-trace.ll (60207 of 60211)
UNSUPPORTED: LLVM :: CodeGen/M68k/CollapseMOVEM.mir (60208 of 60211)
UNSUPPORTED: LLVM :: CodeGen/M68k/multiple-return.ll (60209 of 60211)
UNSUPPORTED: LLVM :: MC/M68k/Relocations/tls.s (60210 of 60211)
FAIL: LLVM :: Transforms/AtomicExpand/AMDGPU/expand-atomic-private-gas.ll (60211 of 60211)
********************
Failed Tests (1):
  LLVM :: Transforms/AtomicExpand/AMDGPU/expand-atomic-private-gas.ll


Testing Time: 169.79s

Total Discovered Tests: 68777
  Excluded   :  2170 (3.16%)
  Skipped    :    16 (0.02%)
  Unsupported:  1038 (1.51%)
  Passed     : 65552 (95.31%)
  Failed     :     1 (0.00%)
FAILED: test/CMakeFiles/check-llvm /b/profcheck-build/build/test/CMakeFiles/check-llvm 
cd /b/profcheck-build/build/test && /usr/bin/python3 /b/profcheck-build/build/./bin/llvm-lit --exclude-xfail /b/profcheck-build/build/test
ninja: build stopped: subcommand failed.
program finished with exit code 1
elapsedTime=253.945958

```

</details>

https://github.com/llvm/llvm-project/pull/154710