[clang] [Basic] Fix crash computing the spelling index of an unknown scoped attribute (PR #208909)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-offload-amdgpu-runtime-2` running on `rocm-worker-hw-02` while building `clang` at step 3 "annotate".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/10/builds/31755

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

```
Step 3 (annotate) failure: 'python ../llvm.src/offload/ci/openmp-offload-amdgpu-libc-runtime.py ...' (failure)
...
PASS: Clang :: CodeGen/SystemZ/zvector.c (8119 of 25707)
PASS: Clang :: CodeGen/SystemZ/zos-mixed-ptr-sizes-sizeof.c (8120 of 25707)
PASS: Clang :: CodeGen/SystemZ/zos-mixed-ptr-sizes-definitions.c (8121 of 25707)
PASS: Clang :: CodeGen/X86/avx512-inline-asm-kregisters-basics.c (8122 of 25707)
PASS: Clang :: CodeGen/WebAssembly/wasm-arguments.c (8123 of 25707)
PASS: Clang :: CodeGen/X86/32bit-behavior-no-eval.c (8124 of 25707)
PASS: Clang :: CodeGen/X86/Float16-complex.c (8125 of 25707)
PASS: Clang :: CodeGen/WebAssembly/builtins-test-fp-sig.c (8126 of 25707)
PASS: Clang :: CodeGen/X86/avx-cxx-record.cpp (8127 of 25707)
PASS: Clang :: CodeGen/X86/32bit-behavior.c (8128 of 25707)
FAIL: Clang :: CodeGen/SystemZ/zos-check-lanuage.c (8129 of 25707)
******************** TEST 'Clang :: CodeGen/SystemZ/zos-check-lanuage.c' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 4
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x c - < /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c | grep -v DIFile > /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x c -
# note: command had no output on stdout or stderr
# executed command: grep -v DIFile
# note: command had no output on stdout or stderr
# RUN: at line 5
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-ast -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-ast -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
# note: command had no output on stdout or stderr
# RUN: at line 6
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x ast - < /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast | grep -v DIFile > /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp2.ll
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x ast -
# note: command had no output on stdout or stderr
# executed command: grep -v DIFile
# note: command had no output on stdout or stderr
# RUN: at line 7
diff /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp2.ll
# executed command: diff /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp2.ll
# note: command had no output on stdout or stderr
# RUN: at line 10
/home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/FileCheck --check-prefix CHECK-C /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c < /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll
# executed command: /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/FileCheck --check-prefix CHECK-C /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
# note: command had no output on stdout or stderr
# RUN: at line 14
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x c++ - < /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c | grep -v DIFile > /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x c++ -
# note: command had no output on stdout or stderr
# executed command: grep -v DIFile
# note: command had no output on stdout or stderr
# RUN: at line 15
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-ast -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast -x c++ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-ast -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast -x c++ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
Step 9 (run check-clang) failure: run check-clang (failure)
...
PASS: Clang :: CodeGen/SystemZ/zvector.c (8119 of 25707)
PASS: Clang :: CodeGen/SystemZ/zos-mixed-ptr-sizes-sizeof.c (8120 of 25707)
PASS: Clang :: CodeGen/SystemZ/zos-mixed-ptr-sizes-definitions.c (8121 of 25707)
PASS: Clang :: CodeGen/X86/avx512-inline-asm-kregisters-basics.c (8122 of 25707)
PASS: Clang :: CodeGen/WebAssembly/wasm-arguments.c (8123 of 25707)
PASS: Clang :: CodeGen/X86/32bit-behavior-no-eval.c (8124 of 25707)
PASS: Clang :: CodeGen/X86/Float16-complex.c (8125 of 25707)
PASS: Clang :: CodeGen/WebAssembly/builtins-test-fp-sig.c (8126 of 25707)
PASS: Clang :: CodeGen/X86/avx-cxx-record.cpp (8127 of 25707)
PASS: Clang :: CodeGen/X86/32bit-behavior.c (8128 of 25707)
FAIL: Clang :: CodeGen/SystemZ/zos-check-lanuage.c (8129 of 25707)
******************** TEST 'Clang :: CodeGen/SystemZ/zos-check-lanuage.c' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 4
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x c - < /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c | grep -v DIFile > /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x c -
# note: command had no output on stdout or stderr
# executed command: grep -v DIFile
# note: command had no output on stdout or stderr
# RUN: at line 5
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-ast -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-ast -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
# note: command had no output on stdout or stderr
# RUN: at line 6
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x ast - < /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast | grep -v DIFile > /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp2.ll
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x ast -
# note: command had no output on stdout or stderr
# executed command: grep -v DIFile
# note: command had no output on stdout or stderr
# RUN: at line 7
diff /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp2.ll
# executed command: diff /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp2.ll
# note: command had no output on stdout or stderr
# RUN: at line 10
/home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/FileCheck --check-prefix CHECK-C /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c < /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll
# executed command: /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/FileCheck --check-prefix CHECK-C /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
# note: command had no output on stdout or stderr
# RUN: at line 14
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x c++ - < /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c | grep -v DIFile > /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp1.ll
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-llvm -S -o - -x c++ -
# note: command had no output on stdout or stderr
# executed command: grep -v DIFile
# note: command had no output on stdout or stderr
# RUN: at line 15
env SDKROOT="/" /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-ast -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast -x c++ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c
# executed command: env SDKROOT=/ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/bin/clang -target s390x-none-zos -emit-ast -o /home/botworker/builds/openmp-offload-amdgpu-runtime-2/build/llvm.build/tools/clang/test/CodeGen/SystemZ/Output/zos-check-lanuage.c.tmp.ast -x c++ /home/botworker/builds/openmp-offload-amdgpu-runtime-2/llvm.src/clang/test/CodeGen/SystemZ/zos-check-lanuage.c

```

</details>

https://github.com/llvm/llvm-project/pull/208909