[Bug target/94791] New: aarch64: -pg profiling is broken with pac-ret

[nsz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94791

            Bug ID: 94791
           Summary: aarch64: -pg profiling is broken with pac-ret
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nsz at gcc dot gnu.org
  Target Milestone: ---

int foo(int x)
{
    return x;
}

gcc -pg -mbranch-protection=pac-ret
gives

foo:
        hint    25 // paciasp
        stp     x29, x30, [sp, -32]!
        mov     x29, sp
        mov     x1, x30
        str     w0, [sp, 28]
        mov     x0, x1  // passing signed return address
        bl      _mcount
        ldr     w0, [sp, 28]
        ldp     x29, x30, [sp], 32
        hint    29 // autiasp
        ret

_mcount needs a valid code address as argument
so different calls from the same call site can
be correlated and the caller can be identified
(e.g. with dladdr). either pac should be removed
with xpaclri or x30 saved into another temp reg
before paciasp.