wrong code generation :

[Dinesh Nagpure <dinesh_nagpure at ivivity dot com>]

Greetings,

While building Linux kernel v 2.4.16 for RM5231A processor I am facing some
problems in the way code is generated for memcpy. I see some unaligned
accesses beging done and also the inline code for memcpy doesn't seem to be
given proper destination address. I also tried the -mmemcpy switch without
much success, here is what I see with -mmemcpy. The offending code is in
console_init( ) as below:

void __init console_init(void)
{

   memset(ldiscs, 0, sizeof(ldiscs));
  (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);

   memset(&tty_std_termios, 0, sizeof(struct termios));
   memcpy(tty_std_termios.c_cc, INIT_C_CC, NCCS);


   printk("tty_std_termios is at %p\n", &tty_std_termios);
		|
		few more printk( ) calls etc.
}


Here is the code generated for the function console_init( )
80206d00 <console_init>:
80206d00:       27bdffc8        addiu   sp,sp,-56
80206d04:       24060400        li      a2,1024
80206d08:       3c048029        lui     a0,0x8029
80206d0c:       2484b140        addiu   a0,a0,-20160
80206d10:       afbf0034        sw      ra,52(sp)
80206d14:       afbe0030        sw      s8,48(sp)
80206d18:       afb7002c        sw      s7,44(sp)
80206d1c:       afb60028        sw      s6,40(sp)
80206d20:       afb50024        sw      s5,36(sp)
80206d24:       afb40020        sw      s4,32(sp)
80206d28:       afb3001c        sw      s3,28(sp)
80206d2c:       afb20018        sw      s2,24(sp)
80206d30:       afb10014        sw      s1,20(sp)
80206d34:       afb00010        sw      s0,16(sp)
80206d38:       3c108029        lui     s0,0x8029
80206d3c:       2610b114        addiu   s0,s0,-20204
80206d40:       0c078bc0        jal     801e2f00 <memset>
80206d44:       00002821        move    a1,zero
80206d48:       3c058022        lui     a1,0x8022
80206d4c:       24a59480        addiu   a1,a1,-27520
80206d50:       0c06117c        jal     801845f0 <tty_register_ldisc>
80206d54:       00002021        move    a0,zero
80206d58:       02002021        move    a0,s0
80206d5c:       00002821        move    a1,zero
80206d60:       0c078bc0        jal     801e2f00 <memset>
80206d64:       24060028        li      a2,40
80206d68:       24060017        li      a2,23
80206d6c:       3c05801f        lui     a1,0x801f
80206d70:       24a5fcc8        addiu   a1,a1,-824
80206d74:       0c0789c8        jal     801e2720 <memcpy>

80206d78:       26040011        addiu   a0,s0,17  /* this bugs me a lot */

80206d7c:       3c04801f        lui     a0,0x801f
80206d80:       2484fcdc        addiu   a0,a0,-804
80206d84:       0c046ddd        jal     8011b774 <printk>
80206d88:       02002821        move    a1,s0
80206d8c:       3c11801f        lui     s1,0x801f
80206d90:       2631fcf8        addiu   s1,s1,-776
80206d94:       92050011        lbu     a1,17(s0)

The destination address for memcpy is c_cc array in the termios structure :

typedef unsigned char cc_t;
typedef unsigned long speed_t;
typedef unsigned long tcflag_t;

/*
 * The ABI says nothing about NCC but seems to use NCCS as
 * replacement for it in struct termio
 */
#define NCCS    23
struct termios {
        tcflag_t c_iflag;               /* input mode flags */
        tcflag_t c_oflag;               /* output mode flags */
        tcflag_t c_cflag;               /* control mode flags */
        tcflag_t c_lflag;               /* local mode flags */

        // cc_t c_cc[NCCS];                /* control characters */

        /*
         * Seems nonexistent in the ABI, but Linux assumes existence ...
         */
        cc_t c_line;                    /* line discipline */
        cc_t c_cc[NCCS];                /* control characters */
};

Source for memcpy( ) is in termios.h as:
#define INIT_C_CC
 
"\003\034\177\025\1\0\0\0\021\023\032\0\022\017\027\026\004\0"

As a result memcpy( ) fails to copy to the destination and c_cc remains all
zeros from memset( ). I see memcpy( ) tries to do some alignment but
apparently fails. If I flip the c_line and c_cc positions then memcpy( )
does work.

I am using gcc-3.0.2 and binutils-2.11.92.0.7. To me this seems to be some
gcc code generation issue. Will someone pls tell me if the toolchain I am
using is good enough or else what should I be using? I don't see any
additional flags also that would slove my problem.

Thanks,
Dinesh