optimization/9383: -fomit-frame-pointer has no effect on nested functions

optimization/9383: -fomit-frame-pointer has no effect on nested functions

[fshvaige]

>Number:         9383
>Category:       optimization
>Synopsis:       -fomit-frame-pointer has no effect on nested functions
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          pessimizes-code
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 21 12:36:00 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator:     fshvaige@cisco.com
>Release:        3.2.1
>Organization:
>Environment:
Configured with: ../gcc-3.2.1/configure --prefix=/home/crossGCC/native --exec_prefix=/home/crossGCC/native --with-local-prefix=/home/crossGCC/native --enable-languages=c,c++ -v

and

Configured with: ../gcc-3.2.1/configure --with-newlib --enable-target-optspace --target=ppc-elf --prefix=/home/crossGCC/ppc-elf --exec_prefix=/home/crossGCC/ppc-elf --with-local-prefix=/home/crossGCC/ppc-elf --program-prefix=ppc-elf- --enable-languages=c,c++ -v
>Description:
File main.c:

extern int h (int func (int));

int g2 (int c) {
        return c;
}

int f (int a, int b) {
        int g1 (int c) {
                return c;
        }
        return h (g1);
}

Command:
gcc -S -Os -fomit-frame-pointer main.c

File main.s:

        .file   "main.c"
        .text
.globl g2
        .type   g2,@function
g2:
        movl    4(%esp), %eax
        ret
.Lfe1:
        .size   g2,.Lfe1-g2
        .type   g1.0,@function
g1.0:
        pushl   %ecx
        movl    8(%esp), %eax
        popl    %edx
        ret
.Lfe2:
        .size   g1.0,.Lfe2-g1.0
.globl f
        .type   f,@function
f:
        subl    $12, %esp
        leal    12(%esp), %ecx
        movl    $g1.0+2, %edx
        movb    $-71, (%esp)
        movl    %esp, %eax
        subl    %ecx, %edx
        movl    %ecx, 1(%esp)
        movb    $-23, 5(%esp)
        movl    %edx, 6(%esp)
        pushl   %eax
        call    h
        addl    $16, %esp
        ret
.Lfe3:
        .size   f,.Lfe3-f
        .ident  "GCC: (GNU) 3.2.1"

Command:
ppc-elf-gcc -S -Os -fomit-frame-pointer main.c

File main.s:

        .file   "main.c"
        .section        ".text"
        .align 2
        .globl g2
        .type   g2,@function
g2:
        blr
.Lfe1:
        .size   g2,.Lfe1-g2
        .align 2
        .type   g1.0,@function
g1.0:
        stwu 1,-16(1)
        addi 1,1,16
        blr
.Lfe2:
        .size   g1.0,.Lfe2-g1.0
        .globl __trampoline_setup
        .align 2
        .globl f
        .type   f,@function
f:
        stwu 1,-64(1)
        lis 5,g1.0@ha
        mflr 0
        la 5,g1.0@l(5)
        addi 3,1,8
        li 4,40
        mr 6,3
        stw 0,68(1)
        crxor 6,6,6
        bl __trampoline_setup
        addi 3,1,8
        bl h
        lwz 0,68(1)
        addi 1,1,64
        mtlr 0
        blr
.Lfe3:
        .size   f,.Lfe3-f
        .ident  "GCC: (GNU) 3.2.1"

Note:
Pay attention to difference between codes generated for function g1() and g2().
>How-To-Repeat:

>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted: