Fu, Chao-Ying wrote:
> Hello,
>
> I think there is a bug in mips_pass_by_reference when the mips abi
> is EABI to pass TImode parameters.
>
>
> The following code is from the mainline GCC "mips.c".
> ---------
> mips_pass_by_reference (CUMULATIVE_ARGS *cum ATTRIBUTE_UNUSED,
> enum machine_mode mode, tree type,
> bool named ATTRIBUTE_UNUSED)
> {
> if (mips_abi == ABI_EABI)
> {
> int size;
>
> /* ??? How should SCmode be handled? */
> if (type == NULL_TREE || mode == DImode || mode == DFmode)
> return 0;
>
> size = int_size_in_bytes (type);
> return size == -1 || size > UNITS_PER_WORD;
> }
> else
> {
> /* If we have a variable-sized parameter, we have no choice. */
> return targetm.calls.must_pass_in_stack (mode, type);
> }
> }
> ---------
> When "type" is NULL_TREE, this function returns "0". But when "type" is
> not NULL and
> the size of TImode is bigger than UNITS_PER_WORD, so it returns "1".
> This causes inconsistency in the following test.
>
> # cat timode.c
> typedef int TItype __attribute__ ((mode (TI)));
> TItype test1 (TItype a)
> {
> return a*a;
> }
>
> # mipsisa64-elf-gcc -S timode.c -O3
>
> ### timiode.s
> test1:
> daddiu $sp,$sp,-8
> sd $31,0($sp)
> ld $3,8($4) <----- Parameter in stack
> ld $2,0($4) <----- Parameter in stack
> move $7,$3 <---- Parameter in register
> move $4,$2 <---- Parameter in register
> move $5,$3 <---- Parameter in register
> jal __multi3
> move $6,$2 <---- Parameter in register
>
> ld $31,0($sp)
> move $4,$2
> move $2,$4
> j $31
> daddiu $sp,$sp,8
>
> Does someone know how to pass TImode parameters in EABI? Thanks!
>
Hi Chao-ying
MIPS ABIs do not usually document the behaviour of 128 bit scalars,
since such types are not defined by most language standards, and are
typically only available via compiler-specific extensions. So if TImode
arguments work correctly on any ABI, then I would guess that it might
be more by luck than design! EABI is one of the more sketchily specified
MIPS ABIs -- the 64-bit variant probably even more so.
You could fix the mips.c back-end to handle TImode consistently for EABI
and post those changes to the appropriate list for comment. But I wonder
if you really need to use EABI, or are only using it because it's the
default for a mipsisa64-elf configuration. If the latter is true, then
you could try using the N32 ABI and see if that works better for you
(i.e. use the --with-abi=n32 argument when configuring your toolchain).
FWIW our own gcc-3.4 mips-sde-elf configurations default to using N32
for 64-bit ISAs, though we've not yet tested that on gcc-4.
Nigel
