[llvm] RuntimeLibcalls: Add stub API for getting function signatures (PR #166290)

[Kewen Meng via llvm-commits]

Kewen12 wrote:

Hello, we see a test failure in our bot. It seems related to this PR. Could you please take a look? Thanks!

bot: https://lab.llvm.org/buildbot/#/builders/10/builds/16663

```
| Input was:
# | <<<<<<
# |             .
# |             .
# |             .
# |           597: declare void @sincospi(...) 
# |           598:  
# |           599: declare void @sincospil(...) 
# |           600:  
# |           601: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: write, errnomem: write) 
# |           602: declare void @__sincosf_stret(ptr sret({ float, float }) align 4, float) #0 
# | check:17'0                                                                                X error: no match found
# |           603:  
# | check:17'0     ~
# |           604: ; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: write, errnomem: write) 
# | check:17'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# |           605: declare void @__sincos_stret(ptr sret({ double, double }) align 8, double) #0 
# | check:17'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# | check:17'1     ?                                                                              possible intended match
# |           606:  
# | check:17'0     ~
# |           607: declare void @sinhf(...) 
# | check:17'0     ~~~~~~~~~~~~~~~~~~~~~~~~~
# |           608:  
# | check:17'0     ~
# |           609: declare void @sinh(...) 
# | check:17'0     ~~~~~~~~~~~~~~~~~~~~~~~~
# |           610:  
# | check:17'0     ~
# |             .
# |             .
# |             .
# | >>>>>>
# `-----------------------------
# error: command failed with exit status: 1
```

https://github.com/llvm/llvm-project/pull/166290