RE: -Os & inlining functions used only once

[David Korn <dkorn at pixelpower dot com>]

>> -finline-functions seems a good candidate but it doesn't appear
>> to works with -Os:
>
>If -Os is active and you also request inlining, the only functions that
>get inlined are those that are so small that the inlined code is about the
>same size as the code to pass the arguments and call the function (meaning
>that we save space no matter how many copies we inline).

  That is precisely the case here, since the inlined code amounts to
replacing  "call _foo" with "movl $1,%eax".  If you replace -Os with -O,
you get the expected results:

---
$ objdump -d a.O.o    [compiled as gcc -O -finline-functions -c a.c]

a.O.o:     file format pe-i386

Disassembly of section .text:

00000000 <_main>:
   0:   55                      push   %ebp
   1:   89 e5                   mov    %esp,%ebp
   3:   83 ec 08                sub    $0x8,%esp
   6:   e8 00 00 00 00          call   b <_main+0xb>
   b:   b8 01 00 00 00          mov    $0x1,%eax
  10:   89 ec                   mov    %ebp,%esp
  12:   5d                      pop    %ebp
  13:   c3                      ret
-----
$ cat a.Os.s        [compiled as gcc -Os -finline-functions -c a.c]
        .file   "a.c"
gcc2_compiled.:
___gnu_compiled_c:
.text
        .align 4
        .def    _foo;   .scl    3;      .type   32;     .endef
_foo:
        pushl %ebp
        movl $1,%eax
        movl %esp,%ebp
        movl %ebp,%esp
        popl %ebp
        ret
        .def    ___main;        .scl    2;      .type   32;     .endef
        .align 4
.globl _main
        .def    _main;  .scl    2;      .type   32;     .endef
_main:
        pushl %ebp
        movl %esp,%ebp
        subl $8,%esp
        call ___main
        call _foo
        movl %ebp,%esp
        popl %ebp
        ret
----


     DaveK
-- 
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