[llvm] [AMDGPU][Attributor] Make `AAAMDFlatWorkGroupSize` honor existing attribute (PR #114357)

[John Tramm via llvm-commits]

jtramm wrote:

The rocm install on this cluster seems to be in a different location, but the `.bc` files don't appear to have either of those attributes in them:

```
jtramm at amdgpu04:/soft/compilers/rocm/rocm-6.3.0/amdgcn/bitcode$ ls
asanrtl.bc                          oclc_isa_version_1010.bc          oclc_isa_version_10-3-generic.bc  oclc_isa_version_600.bc  oclc_isa_version_805.bc  oclc_isa_version_942.bc
hip.bc                              oclc_isa_version_1011.bc          oclc_isa_version_1100.bc          oclc_isa_version_601.bc  oclc_isa_version_810.bc  oclc_isa_version_9-generic.bc
ockl.bc                             oclc_isa_version_1012.bc          oclc_isa_version_1101.bc          oclc_isa_version_602.bc  oclc_isa_version_900.bc  oclc_unsafe_math_off.bc
oclc_abi_version_400.bc             oclc_isa_version_1013.bc          oclc_isa_version_1102.bc          oclc_isa_version_700.bc  oclc_isa_version_902.bc  oclc_unsafe_math_on.bc
oclc_abi_version_500.bc             oclc_isa_version_10-1-generic.bc  oclc_isa_version_1103.bc          oclc_isa_version_701.bc  oclc_isa_version_904.bc  oclc_wavefrontsize64_off.bc
oclc_abi_version_600.bc             oclc_isa_version_1030.bc          oclc_isa_version_1150.bc          oclc_isa_version_702.bc  oclc_isa_version_906.bc  oclc_wavefrontsize64_on.bc
oclc_correctly_rounded_sqrt_off.bc  oclc_isa_version_1031.bc          oclc_isa_version_1151.bc          oclc_isa_version_703.bc  oclc_isa_version_908.bc  ocml.bc
oclc_correctly_rounded_sqrt_on.bc   oclc_isa_version_1032.bc          oclc_isa_version_1152.bc          oclc_isa_version_704.bc  oclc_isa_version_909.bc  opencl.bc
oclc_daz_opt_off.bc                 oclc_isa_version_1033.bc          oclc_isa_version_11-generic.bc    oclc_isa_version_705.bc  oclc_isa_version_90a.bc
oclc_daz_opt_on.bc                  oclc_isa_version_1034.bc          oclc_isa_version_1200.bc          oclc_isa_version_801.bc  oclc_isa_version_90c.bc
oclc_finite_only_off.bc             oclc_isa_version_1035.bc          oclc_isa_version_1201.bc          oclc_isa_version_802.bc  oclc_isa_version_940.bc
oclc_finite_only_on.bc              oclc_isa_version_1036.bc          oclc_isa_version_12-generic.bc    oclc_isa_version_803.bc  oclc_isa_version_941.bc
jtramm at amdgpu04:/soft/compilers/rocm/rocm-6.3.0/amdgcn/bitcode$ grep amdgpu-flat-work-group-size *.bc
jtramm at amdgpu04:/soft/compilers/rocm/rocm-6.3.0/amdgcn/bitcode$ grep amdgpu-waves-per-eu *.bc
jtramm at amdgpu04:/soft/compilers/rocm/rocm-6.3.0/amdgcn/bitcode$ 
```

https://github.com/llvm/llvm-project/pull/114357