Re: [PATCH, MIPS] fix MIPS16 jump table overflow

[Sandra Loosemore <sandra@codesourcery.com>]

On 08/24/2012 11:46 PM, Richard Sandiford wrote:
> Andrew Pinski<pinskia@gmail.com>  writes:
>> On Fri, Aug 24, 2012 at 10:08 PM, Andrew Pinski<pinskia@gmail.com>  wrote:
>>> On Wed, Aug 22, 2012 at 7:15 PM, Sandra Loosemore
>>> <sandra@codesourcery.com>  wrote:
>>>> On 08/21/2012 02:23 PM, Richard Sandiford wrote:
>>>>>
>>>>>
>>>>> Would be nice to add a compile test for -mabi=64 just to make sure
>>>>> that Pmode == DImode works.  A copy of an existing test like
>>>>> code-readable-1.c would be fine.
>>>>
>>>>
>>>> I'm having problems with this part -- it seems like every combination of
>>>> options with -mabi=64 I've tried with code-readable-1.c complains about
>>>> something-or-another being incompatible.  The closest I've come is "-mabi=64
>>>> -march=mips64 -msoft-float", which is accepted by the mipsisa32r2-sde-elf
>>>
>>> Did you test this at all on a mips64-*-* target?  After this change
>>> n64 jump tables are broken.
>>> Before CASE_VECTOR_MODE was DImode for n64 .
>>>
>>> See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54371 for why it fails.
>>> gpdword produces a double word for n64.
>>>
>>> For EABI64 it is ok to load 32bits because that the addresses are
>>> 32bits but for n64, it is not ok.  The load addresses are normally
>>> above the 32bits boundary.
>>
>> I am testing a patch which changes CASE_VECTOR_MODE to be:
>> #define CASE_VECTOR_MODE ((mips_abi == ABI_64) ? DImode : SImode)
>
> I think it should be:
>
> #define CASE_VECTOR_MODE \
>    (TARGET_MIPS16_SHORT_JUMP_TABLES ? SImode : ptr_mode)
>
> #define CASE_VECTOR_SHORTEN_MODE(MIN, MAX, BODY) \
>    (!TARGET_MIPS16_SHORT_JUMP_TABLES ? ptr_mode \
>     : (MIN)>= -32768&&  (MAX)<  32768 : HImode \
>     : SImode)
>
> The point being that the TARGET_MIPS16_SHORT_JUMP_TABLES entries
> are relative, so SImode would be correct there even for n64.
>
> I'd missed that CASE_VECTOR_MODE applied to tablejump as well
> as casesi, sorry.

Yeah, sorry.  :-(  The original version of the patch I posted (where 
CASE_VECTOR_MODE was #defined to ptr_mode) had indeed been tested on 
mips64, but not the revised version that was approved for check-in.

-Sandra