[llvm] [WebAssembly] Print type signature and table for call_indirect (PR #179120)

[Heejin Ahn via llvm-commits]

aheejin wrote:

> Adding the reference-types attribute does not cause an error.
> 
> ```
> 
> $ bin/llvm-mc -triple=wasm32 -mattr=+tail-call,+reference-types -show-encoding tail.s
>         .file   "tail.ll"
>         .tabletype      __indirect_function_table, funcref
>         .functype       indirect_musttail (i32, i32) -> (i32)
>         .section        .text.indirect_musttail,"",@
>         .globl  indirect_musttail
> indirect_musttail:
>         .functype       indirect_musttail (i32, i32) -> (i32)
>         local.get       0                       # encoding: [0x20,0x00]
>         local.get       1                       # encoding: [0x20,0x01]
>         local.get       0                       # encoding: [0x20,0x00]
>         return_call_indirect     __indirect_function_table, (i32, i32) -> (i32) # encoding: [0x13,0x80'A',0x80'A',0x80'A',0x80'A',A,0x80'B',0x80'B',0x80'B',0x80'B',B]
>                                         #   fixup A - offset: 1, value: .Ltypeindex0 at TYPEINDEX, kind: fixup_uleb128_i32
>                                         #   fixup B - offset: 6, value: __indirect_function_table, kind: fixup_uleb128_i32
>         end_function                            # encoding: [0x0b]
>         .section        .custom_section.target_features,"",@
>         
> ```

The reason `llc` prints `__indirect_function_table` without `-mattr=+reference-types` but `llvm-mc` cannot parse it without it was, `llc` was using `generic` CPU by default, but `llvm-mc` was not.
https://github.com/llvm/llvm-project/blob/75f738b0b2a15281c6f285380ea947e973a6e02f/llvm/lib/Target/WebAssembly/WebAssembly.td#L129-L139

For consistency, I updated `llvm-mc` to use `generic` CPU as well in #181460. This isn't necessarily related to this PR though.

https://github.com/llvm/llvm-project/pull/179120