[Bug target/116174] New: Alignment request is added before endbr with -fcf-protection=branch

[gcc at breakpoint dot cc via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116174

            Bug ID: 116174
           Summary: Alignment request is added before endbr with
                    -fcf-protection=branch
           Product: gcc
           Version: 14.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at breakpoint dot cc
  Target Milestone: ---

The file lib_str.c:

char *stpcpy(char *dest, const char *src)
{
        while ((*dest++ = *src++) != '\0')
                /* nothing */;
        return --dest;
}

----
 gcc -nostdinc -fno-common -fno-PIE \
         -fcf-protection=branch -fno-jump-tables -m64 -falign-jumps=1
-falign-loops=1 \
         -fno-asynchronous-unwind-tables -mindirect-branch=thunk-extern \
         -mfunction-return=thunk-extern -O2 \
         -S -o lib_str.s lib_str.c
-----

Output:
        .text
        .p2align 4
        .globl  stpcpy
        .type   stpcpy, @function
stpcpy: 
        .p2align 5
        endbr64
.L2:
        movzbl  (%rsi), %eax
…
------

The problem is that this .p2align macro before endbr64 results in 16 nops (11
byte nop + 5 byte nop) before endbr on function entry.

I see this with 
- gcc version 14.1.0 (Debian 14.1.0-5) 
- gcc version 15.0.0 20240717 (experimental) [master r15-2089-gecc2c3cb723]
(Debian 20240717-1) 

I don't see this with gcc-13.

Sebastian