[llvm] [Attributor] Use known non-flat AS before `getAssumedAddrSpace` (PR #143221)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

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

Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/27180

<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 :: Transforms/OpenMP/spmdization_no_guarding_two_reaching_kernels.ll' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/opt -S -passes=openmp-opt < /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/test/Transforms/OpenMP/spmdization_no_guarding_two_reaching_kernels.ll | /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/FileCheck /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/test/Transforms/OpenMP/spmdization_no_guarding_two_reaching_kernels.ll --check-prefixes=CHECK # RUN: at line 2
+ /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/FileCheck /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/test/Transforms/OpenMP/spmdization_no_guarding_two_reaching_kernels.ll --check-prefixes=CHECK
+ /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/opt -S -passes=openmp-opt
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/build/bin/opt: WARNING: failed to create target machine for 'nvptx64': unable to get target for 'nvptx64', see --version and --triple.
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/test/Transforms/OpenMP/spmdization_no_guarding_two_reaching_kernels.ll:284:15: error: CHECK-NEXT: expected string not found in input
; CHECK-NEXT: [[TMP0:%.*]] = addrspacecast ptr [[DOTGLOBAL_TID__ADDR]] to ptr addrspace(5)
              ^
<stdin>:106:41: note: scanning from here
 %.bound_tid..addr = alloca ptr, align 8
                                        ^
<stdin>:106:41: note: with "DOTGLOBAL_TID__ADDR" equal to "%\\.global_tid\\.\\.addr"
 %.bound_tid..addr = alloca ptr, align 8
                                        ^
<stdin>:111:4: note: possible intended match here
; Function Attrs: noinline norecurse nounwind
   ^
/home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/test/Transforms/OpenMP/spmdization_no_guarding_two_reaching_kernels.ll:317:15: error: CHECK-NEXT: expected string not found in input
; CHECK-NEXT: [[TMP2:%.*]] = addrspacecast ptr [[DOTADDR]] to ptr addrspace(5)
              ^
<stdin>:117:36: note: scanning from here
 %global_args = alloca ptr, align 8
                                   ^
<stdin>:117:36: note: with "DOTADDR" equal to "%\\.addr"
 %global_args = alloca ptr, align 8
                                   ^
<stdin>:119:29: note: possible intended match here
 call void @__omp_outlined__(ptr %.addr1, ptr %.zero.addr) #8
                            ^

Input file: <stdin>
Check file: /home/buildbot/buildbot-root/llvm-clang-x86_64-sie-ubuntu-fast/llvm-project/llvm/test/Transforms/OpenMP/spmdization_no_guarding_two_reaching_kernels.ll

-dump-input=help explains the following input dump.

Input was:
<<<<<<
             1: ; ModuleID = '<stdin>' 
             2: source_filename = "<stdin>" 
             3: target datalayout = "e-i64:64-i128:128-v16:16-v32:32-n16:32:64" 
             4: target triple = "nvptx64" 
             5:  
             6: %struct.ident_t = type { i32, i32, i32, i32, ptr } 
             7: %struct.KernelEnvironmentTy = type { %struct.ConfigurationEnvironmentTy, ptr, ptr } 
             8: %struct.ConfigurationEnvironmentTy = type { i8, i8, i8, i32, i32, i32, i32, i32, i32 } 
             9:  
...

```

</details>

https://github.com/llvm/llvm-project/pull/143221