[patch] Hookize SMALL_REGISTER_CLASSES

[Alexander Strange]

On May 2, 2010, at 6:07 PM, Steven Bosscher wrote:

> Take 4. The spam filter is apparently convinced that this patch is
> spam. Trying as .gz now...
> 
> On Sun, May 2, 2010 at 10:42 PM, Steven Bosscher <stevenb dot gcc at
> gmail dot com> wrote:
>> Hi,
>> 
>> This is a re-post of
>> http://gcc.gnu.org/ml/gcc-patches/2008-12/msg00590.html for GCC 4.6.
>> 
>> The actual purpose of this patch is to make it possible to have
>> SMALL_REGISTER_CLASSES be false for some register classes but not for
>> all.
>> 
>> In the current situation, SMALL_REGISTER_CLASSES is true or false, but
>> targets are not black and white.  For x86-64, I've noticed we often
>> get better results with floating point code if I disable
>> SMALL_REGISTER_CLASSES, but it also results in lots of trouble with
>> INTEGRAL_MODE_P modes (similar to what happens if you enable
>> scheduling for x86-64).
>> 
>> With the patch, a target can choose to allow more optimizations when
>> it has good reason to believe that registers in some machine modes
>> will not be allocated to small register classes.
>> 
>> Bootstrapped&tested on x86_64-unknown-linux-gnu.
>> OK for trunk?

> +  /* AMD64 has 16 registers for >=32 bits integers.  This is not
> +     large compared to RISC/VLIW architectures, but it is big
> +     enough for us to consider it non-small.  */
> +  if (SCALAR_INT_MODE_P (mode) && GET_MODE_SIZE (mode) >= 32)
> +    return false;


The new registers in AMD64 all have 8- and 16-bit subregs, so those register classes are just as large.
Although gcc always seems to do operations in at least 32-bit on x86 anyway, so this probably doesn't matter...


>> 
>> Ciao!
>> Steven
>> 
>>        * doc/tm.texi (defmac SMALL_REGISTER_CLASSES): Remove.
>>        (TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P): Add documentation,
>>        based on the above, for new target hook.
>> 
>>        * hooks.c (hook_bool_mode_true): New generic hook.
>>        * hooks.h (hook_bool_mode_true): Add prototype.
>> 
>>        * target.h (struct gcc_target): Add small_register_classes_for_mode_p
>>        target hook.
>>        * target-def.h (TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P): New default
>>        target hook, set to hook_bool_mode_false.
>>        * regs.h: Remove default definition of SMALL_REGISTER_CLASSES.
>>        * reload.c (push_secondary_reload): Replace SMALL_REGISTER_CLASSES
>>        with targetm.small_register_classes_for_mode_p.
>>        (find_reusable_reload): Likewise.
>>        (combine_reloads): Likewise.
>>        * reload1.c (reload_as_needed): Likewise.
>>        * cse.c (approx_reg_cost_1, hash_rtx_cb): Likewise.
>>        * ifcvt.c (noce_process_if_block, check_cond_move_block,
>>        dead_or_predicable): Likewise.
>>        * regmove.c (optimize_reg_copy_1): Likewise.
>>        * calls.c (prepare_call_address): Likewise.
>>        (precompute_register_parameters): Likewise.
>> 
>>        * config/i386/i386.h: Replace SMALL_REGISTER_CLASSES with new target
>>        hook definition.
>>        * config/i386/i386.c (ix86_small_register_classes_for_mode_p): Add
>>        implementation of the hook that considers SSE and 64-bit integer
>>        register classes "not small".
>>        * config/i386/i386-protos.h (ix86_small_register_classes_for_mode_p):
>>        Add prototype.
>> 
>>        * config/sh/sh.h: Replace SMALL_REGISTER_CLASSES with new target
>>        hook definition.
>>        * config/sh/sh.c (sh_small_register_classes_for_mode_p): Add
>>        implementation of the hook that considers all register classes
>>        small except for SH64.
>>        (sh_override_options): Use the new hook.
>>        * config/sh/sh-protos.h (sh_small_register_classes_for_mode_p):
>>        Add prototype.
>> 
>>        * config/arm/arm.h: Replace SMALL_REGISTER_CLASSES with new target
>>        hook definition.
>>        * config/arm/arm.c (arm_small_register_classes_for_mode_p): Add
>>        implementation of the hook that considers all register classes
>>        small for THUMB1.
>>        * config/arm/arm-protos.h (arm_small_register_classes_for_mode_p):
>>        Add prototype.
>> 
>>        * config/mips/mips.h: Replace SMALL_REGISTER_CLASSES with new target
>>        hook definition.
>>        * config/mips/mips.c (mips_small_register_classes_for_mode_p): Add
>>        implementation of the hook that considers all register classes
>>        small for MIPS16.
>>        * config/mips/mips-protos.h (mips_small_register_classes_for_mode_p):
>>        Add prototype.
>> 
>>        * config/m32c/m32c.h: Replace SMALL_REGISTER_CLASSES with new target
>>        hook definition.
>>        * config/pdp11/pdp11.h: Likewise.
>>        * config/avr/avr.h: Likewise.
>>        * config/xtensa/xtensa.h: Likewise.
>>        * config/m68hc11/m68hc11.h: Likewise.
>>        * config/mn10300/mn10300.h: Likewise.
>>        * config/mcore/mcore.h: Likewise.
>>        * config/h8300/h8300.h: Likewise.
>>        * config/bfin/bfin.h: Likewise.
>> 
>>        * config/iq2000/iq2000.h: Remove SMALL_REGISTER_CLASSES definition.
>>        * config/rx/rx.h: Remove SMALL_REGISTER_CLASSES definition.
>> 
> <hookize_SMALL_REGISTER_CLASSES.diff.gz>