[MIPS] One test failed

[Fu, Chao-Ying]

Hi,

  I got one test that failed by using the mainline GCC
on the target of mipsisa32r2-elf.
The handling of stack pointer or frame pointer may be broken.
Thanks!

Ex:
# mipsisa32r2-elf-gcc -o bug126 -Tidt32.ld bug126.c
# mipsisa32r2-elf-run bug126
mips-core: 4 byte read to unmapped address 0x4 at 0x80020348
program stopped with signal 10.
# cat bug126.c
int check_var (int z, ...)
{
}

int main ()
{
  check_var (2);
  return 0;
}

(big126.s)
check_var:
        .frame  $fp,80,$31
        .mask   0x40000000,-4
        .fmask  0x00000000,0
        .set    noreorder
        .set    nomacro

        addiu   $sp,$sp,-80
        sw      $fp,76($sp) <----------
        move    $fp,$sp
        sw      $5,52($fp)
        sw      $6,56($fp)
        sw      $7,60($fp)
        sw      $8,64($fp)
        sw      $9,68($fp)
        sw      $10,72($fp)
        sw      $11,76($fp)  <---------- Data is written again.
        sdc1    $f12,16($fp)
        sdc1    $f14,24($fp)
        sdc1    $f16,32($fp)
        sdc1    $f18,40($fp)
        sw      $4,0($fp)
        move    $sp,$fp
        lw      $fp,76($sp)  <---------- FP is wrong.
        addiu   $sp,$sp,80
        j       $31
        nop

        .set    macro
        .set    reorder
        .end    check_var
        .size   check_var, .-check_var
        .align  2
        .globl  main
        .ent    main
main:
        .frame  $fp,8,$31
        .mask   0xc0000000,-4
        .fmask  0x00000000,0
        .set    noreorder
        .set    nomacro

        addiu   $sp,$sp,-8
        sw      $31,4($sp)
        sw      $fp,0($sp)
        move    $fp,$sp
        li      $4,2
        jal     check_var
        nop

        move    $2,$0
        move    $sp,$fp <----------- SP is wrong.
        lw      $31,4($sp) <---------- FAIL
        lw      $fp,0($sp)
        addiu   $sp,$sp,8
        j       $31
        nop

Regards,
Chao-ying