[EMAIL PROTECTED] gujin]$ cat tmp.c
#include <string.h>
typedef struct {
unsigned short data[3];
union diskcmd {
unsigned udata[5];
unsigned char cdata[20];
} cmd;
} bootloader2_t;
bootloader2_t uninstall_mbr;
extern inline unsigned char
BOOT1_diskread (union diskcmd *str, unsigned buffer)
{
unsigned short status, dummy;
unsigned char returned;
asm volatile (
" movw %%es,%%ax \n"
" pushl %4 \n"
" popw %%bx \n"
" popw %%es \n"
" pushw %%ax \n"
" callw read_disk \n"
" popw %%es \n"
" setc %%dl # set dest to 1 if carry, else clear dest \n"
: "=&a" (status), "=d" (returned), "=S" (dummy)
: "S" (str), "g" (buffer), "d" (str->cdata[2]), "X" (*str)
: "ebx", "edi", "ecx", "memory"
);
return returned;
}
unsigned char BOOT1_uninstall_mbr (void)
{
bootloader2_t copy_in_dataseg;
memcpy (©_in_dataseg, &uninstall_mbr, sizeof (bootloader2_t));
return (BOOT1_diskread (©_in_dataseg.cmd, 0x00007c00) != 0);
}
[EMAIL PROTECTED] gujin]$ /home/etienne/projet/toolchain-2.95.3/bin/gcc
-fomit-frame-pointer -mrtd -Os -c -o tmp.o tmp.c && size tmp.o
text data bss dec hex filename
69 0 0 69 45 tmp.o
[EMAIL PROTECTED] gujin]$ /home/etienne/projet/toolchain-3.4.5/bin/gcc
-fomit-frame-pointer -mrtd -Os -c -o tmp.o tmp.c && size tmp.o
text data bss dec hex filename
67 0 0 67 43 tmp.o
[EMAIL PROTECTED] gujin]$ /home/etienne/projet/toolchain-4.1.1/bin/gcc
-fomit-frame-pointer -mrtd -Os -c -o tmp.o tmp.c && size tmp.o
text data bss dec hex filename
93 0 0 93 5d tmp.o
[EMAIL PROTECTED] gujin]$ /home/etienne/projet/toolchain-4.1.1/bin/gcc
-fomit-frame-pointer -mrtd -Os -S -o tmp.s tmp.c
[EMAIL PROTECTED] gujin]$ cat tmp.s
.file "tmp.c"
.text
.globl BOOT1_uninstall_mbr
.type BOOT1_uninstall_mbr, @function
BOOT1_uninstall_mbr:
pushl %edi
pushl %esi
pushl %ebx
subl $56, %esp
leal 8(%esp), %eax
pushl $28
pushl $uninstall_mbr
pushl %eax
call memcpy
movb 18(%esp), %al
leal 16(%esp), %esi
movb %al, 7(%esp)
leal 36(%esp), %eax
pushl $20
pushl %esi
pushl %eax
call memcpy
movb 7(%esp), %dl
#APP
movw %es,%ax
pushl $31744
popw %bx
popw %es
pushw %ax
callw read_disk
popw %es
setc %dl # set dest to 1 if carry, else clear dest
#NO_APP
xorl %eax, %eax
testb %dl, %dl
movb %dl, 3(%esp)
setne %al
addl $56, %esp
popl %ebx
popl %esi
popl %edi
ret
.size BOOT1_uninstall_mbr, .-BOOT1_uninstall_mbr
.comm uninstall_mbr,28,4
.ident "GCC: (GNU) 4.1.1"
.section .note.GNU-stack,"",@progbits
Note the _two_ memcpy, a temporary is created identical of "copy_in_dataseg",
even if "copy_in_dataseg" could be used without problem.
If using the -O2 optimisation, the second memcpy() is inlined - but nothing
more.
--
Summary: temporary created for unknown reason
Product: gcc
Version: 4.1.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: etienne_lorrain at yahoo dot fr
GCC build triplet: i686-pc-linux-gnu
GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29029
