__builtin_frame_address on MIPS

[Ranjit Deshpande]

Hello,

It seems as if __builtin_return_address() with arguments > 1 does not work
correctly on GCC 3.3.x. My compiler version is 3.3.4.

Here is a snippet of the source code:

int boo()
{
        int i = 10; /* Create a local variable */
        printf("%p\n", __builtin_frame_address(1));
}

int main()
{
        boo();
}

Here's the assembly code that gets generated:

00400840 <boo>:
  400840:       3c1c0fc0        lui     gp,0xfc0
  400844:       279c77e0        addiu   gp,gp,30688
  400848:       0399e021        addu    gp,gp,t9
  40084c:       27bdffd8        addiu   sp,sp,-40
  400850:       afbc0010        sw      gp,16(sp)
  400854:       afbf0020        sw      ra,32(sp)
  400858:       afbe001c        sw      s8,28(sp) <====== old FP
  40085c:       afbc0018        sw      gp,24(sp)
  400860:       03a0f021        move    s8,sp <===== new FP
  400864:       8fc20000        lw      v0,0(s8) <===== get old FP
  400868:       8f84801c        lw      a0,-32740(gp)
  40086c:       00000000        nop
  400870:       24840a80        addiu   a0,a0,2688
  400874:       00402821        move    a1,v0
  400878:       8f99804c        lw      t9,-32692(gp)
  40087c:       00000000        nop
  400880:       0320f809        jalr    t9 /* printf */

>From the disassembly above, it seems that __builtin_frame_address(1) assumes
that the previous frame pointer is at offset 0 in the current stack frame,
but the code to save the previous frame pointer puts it at offset 28 within
the stack frame. Obviously, the output printed by the C code is wrong.

Has this problem been addressed in gcc 3.4.x ? I confess that I have not
checked if this is fixed in the 3.4.x series.

Thanks,
-Ranjit