[Bug inline-asm/20712] New: asm code depends on position of function in the source

[y_s_r at list dot ru]

The following 3 equvalent variants of the same primitive program should lead to
the same code, but they don't:

1. C source:

static inline int f1();
static inline int f2();

int main() { f1(); }
static inline int f1() { f2(); }
static inline int f2() { return 1; }

Its assembler output:

        .file   "main_1.c"
        .version        "01.01"
gcc2_compiled.:
.text
        .align 4
.globl main
        .type    main,@function
main:
        pushl   %ebp
        movl    %esp, %ebp
        pushl   %eax
        pushl   %eax
        leave
        jmp     f1
.Lfe1:
        .size    main,.Lfe1-main
        .align 4
        .type    f1,@function
f1:
        pushl   %ebp
        movl    %esp, %ebp
        pushl   %edx
        pushl   %edx
        leave
        jmp     f2
.Lfe2:
        .size    f1,.Lfe2-f1
        .align 4
        .type    f2,@function
f2:
        pushl   %ebp
        movl    $1, %eax
        movl    %esp, %ebp
        popl    %ebp
        ret
.Lfe3:
        .size    f2,.Lfe3-f2
        .ident  "GCC: (GNU) 2.96 20000731 (Red Hat Linux 7.3 2.96-110)"

2. C source:

static inline int f1();
static inline int f2();

int main() { f1(); }
static inline int f2() { return 1; }
static inline int f1() { f2(); }

Its assembler output:

        .file   "main_2.c"
        .version        "01.01"
gcc2_compiled.:
.text
        .align 4
.globl main
        .type    main,@function
main:
        pushl   %ebp
        movl    %esp, %ebp
        pushl   %eax
        pushl   %eax
        leave
        jmp     f1
.Lfe1:
        .size    main,.Lfe1-main
        .align 4
        .type    f1,@function
f1:
        pushl   %ebp
        movl    %esp, %ebp
        popl    %ebp
        ret
.Lfe2:
        .size    f1,.Lfe2-f1
        .ident  "GCC: (GNU) 2.96 20000731 (Red Hat Linux 7.3 2.96-110)"

3. C source:

static inline int f1();
static inline int f2();

static inline int f2() { return 1; }
static inline int f1() { f2(); }
int main() { f1(); }

Its assembler output:

        .file   "main_3.c"
        .version        "01.01"
gcc2_compiled.:
.text
        .align 4
.globl main
        .type    main,@function
main:
        pushl   %ebp
        movl    %esp, %ebp
        popl    %ebp
        ret
.Lfe1:
        .size    main,.Lfe1-main
        .ident  "GCC: (GNU) 2.96 20000731 (Red Hat Linux 7.3 2.96-110)"

In the C code automatically generated by the nesC compiler such a situation
leads to significant missing of optimization for size.

-- 
           Summary: asm code depends on position of function in the source
           Product: gcc
           Version: 2.96
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P2
         Component: inline-asm
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: y_s_r at list dot ru
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux
  GCC host triplet: i686-pc-linux
GCC target triplet: i686-pc-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20712