[Bug target/110132] New: aarch64: Bogus -Wbuiltin-declaration-mismatch with ls64 builtins

["acoplan at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110132

            Bug ID: 110132
           Summary: aarch64: Bogus -Wbuiltin-declaration-mismatch with
                    ls64 builtins
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: acoplan at gcc dot gnu.org
  Target Milestone: ---

If one subverts arm_acle.h and tries to create a minimal preprocessed test case
using ls64 builtins:

$ cat ls64.i
#pragma GCC aarch64 "arm_acle.h"
typedef __arm_data512_t data512_t;
void f(void *p, data512_t d) {
  __builtin_aarch64_st64b(p, d);
}
./xgcc -B . -c ls64.i -S -o /dev/null -march=armv8.7-a
ls64.i: In function ‘f’:
ls64.i:4:3: warning: implicit declaration of function ‘__builtin_aarch64_st64b’
[-Wimplicit-function-declaration]
    4 |   __builtin_aarch64_st64b(p, d);
      |   ^~~~~~~~~~~~~~~~~~~~~~~
ls64.i:4:3: warning: incompatible implicit declaration of built-in function
‘__builtin_aarch64_st64b’ [-Wbuiltin-declaration-mismatch]

we get these bogus warnings. The normal flow for e.g. Advanced SIMD builtins
is:
 - Backend calls add_builtin_function.
 - c_builtin_function adds the builtin to the list of visible_builtins.
 - push_file_scope gets called and builtins in visible_builtins are made
visible.

The problem here is that aarch64_init_ls64_builtins is called when processing
the pragma for arm_acle.h, which is *after* push_file_scope gets called, so the
builtins never get made visible by the C FE.

I think it might be easiest to make the ls64 handling more SVE-like and use the
simulate_builtin_function_decl langhook (which doesn't have this deferred
visibility situation), dropping the wrapper functions from arm_acle.h
altogether.