[Bug middle-end/121673] New: Missed optimization for arguments of calls to the same function

[antoshkka at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121673

            Bug ID: 121673
           Summary: Missed optimization for arguments of calls to the same
                    function
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: antoshkka at gmail dot com
  Target Milestone: ---

Consider the example:

int func(int);

int test(bool cond) {
    return cond ? func(1) : func(2);  
}

GCC generates the following assembly:

"test(bool)":
        test    dil, dil
        je      .L2
        mov     edi, 1
        jmp     "func(int)"
.L2:
        mov     edi, 2
        jmp     "func(int)"

However a more compact and efficient assembly is possible:

test(bool):
        mov     eax, 2
        sub     eax, edi
        mov     edi, eax
        jmp     func(int)@PLT


Godbolt playground https://godbolt.org/z/qrnz4TPfP