Ping. Originaly message was here:
https://gcc.gnu.org/ml/gcc-patches/2014-07/msg01113.html
Richard Sandiford <rdsandif...@googlemail.com> writes:
> Richard Sandiford <rdsandif...@googlemail.com> writes:
>> Jan Hubicka <hubi...@ucw.cz> writes:
>>> Hi,
>>
>>> IRA initialization shows high in profiles even when building lto
>>> objects. This patch simply delays RTL backend initialization until we
>>> really decide to output a function. In some cases this avoids the
>>> initialization completely (like in the case of LTO but also user
>>> target attributes) and there is some hope for better cache locality.
>>>
>>> Basic idea is to have two flags saying whether lang and target
>>> dependent bits needs initialization and check it when starting
>>> function codegen.
>>>
>>> Bootstrapped/regtested x86_64-linux, testing also at AIX. Ok if it passes?
>>>
>>> Honza
>>>
>>> * toplev.c (backend_init_target): Move init_emit_regs and init_regs
>>> to...
>>> (backend_init) ... here; skip ira_init_once and backend_init_target.
>>> (target_reinit) ... and here; clear
>>> this_target_rtl->lang_dependent_initialized.
>>> (lang_dependent_init_target): Clear
>>> this_target_rtl->lang_dependent_initialized;
>>> break out rtl initialization to ...
>>> (initialize_rtl): ... here; call also backend_init_target and
>>> ira_init_once.
>>> * toplev.h (initialize_rtl): New function.
>>> * function.c: Include toplev.h
>>> (init_function_start): Call initialize_rtl.
>>> * rtl.h (target_rtl): Add target_specific_initialized,
>>> lang_dependent_initialized.
>>> Index: toplev.c
>>> ===================================================================
>>> --- toplev.c (revision 211837)
>>> +++ toplev.c (working copy)
>>> @@ -1583,14 +1583,6 @@ backend_init_target (void)
>>> /* Initialize alignment variables. */
>>> init_alignments ();
>>>
>>> - /* This reinitializes hard_frame_pointer, and calls
>>> init_reg_modes_target()
>>> - to initialize reg_raw_mode[]. */
>>> - init_emit_regs ();
>>> -
>>> - /* This invokes target hooks to set fixed_reg[] etc, which is
>>> - mode-dependent. */
>>> - init_regs ();
>>> -
>>> /* This depends on stack_pointer_rtx. */
>>> init_fake_stack_mems ();
>>>
>>> @@ -1632,9 +1624,13 @@ backend_init (void)
>>> init_varasm_once ();
>>> save_register_info ();
>>>
>>> - /* Initialize the target-specific back end pieces. */
>>> - ira_init_once ();
>>> - backend_init_target ();
>>> + /* Middle end needs this initialization for default mem attributes
>>> + used by early calls to make_decl_rtl. */
>>> + init_emit_regs ();
>>> +
>>> + /* Middle end needs this initialization for mode tables used to assign
>>> + modes to vector variables. */
>>> + init_regs ();
>>
>> This causes a segfault on gcc.target/mips/umips-store16-1.c. The register
>> asm:
>>
>> register unsigned int global asm ("$16");
>>
>> causes us to globalise $16 and call reinit_regs. reinit_regs in turn
>> calls ira_init, but IRA hasn't been initialised at this point and
>> prerequisites like init_fake_stack_mems haven't yet been called.
>>
>> Does the patch below look OK?
>>
>>> @@ -1686,6 +1682,31 @@ lang_dependent_init_target (void)
>>> front end is initialized. It also depends on the HAVE_xxx macros
>>> generated from the target machine description. */
>>> init_optabs ();
>>> + this_target_rtl->lang_dependent_initialized = false;
>>> +}
>>> +
>>> +/* Perform initializations that are lang-dependent or target-dependent.
>>> + but matters only for late optimizations and RTL generation. */
>>> +
>>> +void
>>> +initialize_rtl (void)
>>> +{
>>> + static int initialized_once;
>>> +
>>> + /* Initialization done just once per compilation, but delayed
>>> + till code generation. */
>>> + if (!initialized_once)
>>> + ira_init_once ();
>>> + initialized_once = true;
>>> +
>>> + /* Target specific RTL backend initialization. */
>>> + if (!this_target_rtl->target_specific_initialized)
>>> + backend_init_target ();
>>> + this_target_rtl->target_specific_initialized = true;
>>> +
>>> + if (this_target_rtl->lang_dependent_initialized)
>>> + return;
>>> + this_target_rtl->lang_dependent_initialized = true;
>>>
>>> /* The following initialization functions need to generate rtl, so
>>> provide a dummy function context for them. */
>>
>> Why do you need both these flags? We only call this function once
>> the language has been initialised, so we should always be initialising
>> both sets of information (backend_init_target and the stuff after
>> the comment above, from the old lang_dependent_init_target).
>>
>> How about the second patch below, still under testing? The new assert
>> is OK for target_reinit because it has:
>>
>> this_target_rtl->target_specific_initialized = false;
>>
>> /* This initializes hard_frame_pointer, and calls init_reg_modes_target()
>> to initialize reg_raw_mode[]. */
>> init_emit_regs ();
>>
>> /* This invokes target hooks to set fixed_reg[] etc, which is
>> mode-dependent. */
>> init_regs ();
>>
>> /* Reinitialize lang-dependent parts. */
>> lang_dependent_init_target ();
>>
>> i.e. it sets the flag to say that the RTL stuff hasn't been initialised
>> and then goes on to initialise everything that needs to be deferred.
>
> Now tested on mips64-linux-gnu. OK for both patches?
>
>> Thanks,
>> Richard
>>
>>
>> gcc/
>> PR rtl-optimization/61629
>> * reginfo.c (reinit_regs): Only call ira_init and recog_init if
>> they have already been initialized.
>>
>> Index: gcc/reginfo.c
>> ===================================================================
>> --- gcc/reginfo.c 2014-07-16 07:59:00.039669668 +0100
>> +++ gcc/reginfo.c 2014-07-16 07:59:00.397672987 +0100
>> @@ -533,8 +533,11 @@ reinit_regs (void)
>> init_regs ();
>> /* caller_save needs to be re-initialized. */
>> caller_save_initialized_p = false;
>> - ira_init ();
>> - recog_init ();
>> + if (this_target_rtl->target_specific_initialized)
>> + {
>> + ira_init ();
>> + recog_init ();
>> + }
>> }
>>
>> /* Initialize some fake stack-frame MEM references for use in
>>
>>
>> gcc/
>> * rtl.h (target_rtl): Remove lang_dependent_initialized.
>> * toplev.c (initialize_rtl): Don't use it. Move previously
>> "language-dependent" calls to...
>> (backend_init): ...here.
>> (lang_dependent_init_target): Don't set lang_dependent_initialized.
>> Assert that RTL initialization hasn't happend yet.
>>
>> Index: gcc/rtl.h
>> ===================================================================
>> --- gcc/rtl.h 2014-07-11 11:55:14.265158363 +0100
>> +++ gcc/rtl.h 2014-07-16 08:16:23.245370141 +0100
>> @@ -2517,7 +2517,6 @@ struct GTY(()) target_rtl {
>>
>> /* Track if RTL has been initialized. */
>> bool target_specific_initialized;
>> - bool lang_dependent_initialized;
>> };
>>
>> extern GTY(()) struct target_rtl default_target_rtl;
>> Index: gcc/toplev.c
>> ===================================================================
>> --- gcc/toplev.c 2014-07-11 11:54:41.604838961 +0100
>> +++ gcc/toplev.c 2014-07-16 08:22:36.226034738 +0100
>> @@ -1604,6 +1604,10 @@ backend_init_target (void)
>> on a mode change. */
>> init_expmed ();
>> init_lower_subreg ();
>> + init_set_costs ();
>> +
>> + init_expr_target ();
>> + ira_init ();
>>
>> /* We may need to recompute regno_save_code[] and regno_restore_code[]
>> after a mode change as well. */
>> @@ -1682,7 +1686,8 @@ lang_dependent_init_target (void)
>> front end is initialized. It also depends on the HAVE_xxx macros
>> generated from the target machine description. */
>> init_optabs ();
>> - this_target_rtl->lang_dependent_initialized = false;
>> +
>> + gcc_assert (!this_target_rtl->target_specific_initialized);
>> }
>>
>> /* Perform initializations that are lang-dependent or target-dependent.
>> @@ -1701,26 +1706,10 @@ initialize_rtl (void)
>>
>> /* Target specific RTL backend initialization. */
>> if (!this_target_rtl->target_specific_initialized)
>> - backend_init_target ();
>> - this_target_rtl->target_specific_initialized = true;
>> -
>> - if (this_target_rtl->lang_dependent_initialized)
>> - return;
>> - this_target_rtl->lang_dependent_initialized = true;
>> -
>> - /* The following initialization functions need to generate rtl, so
>> - provide a dummy function context for them. */
>> - init_dummy_function_start ();
>> -
>> - /* Do the target-specific parts of expr initialization. */
>> - init_expr_target ();
>> -
>> - /* Although the actions of these functions are language-independent,
>> - they use optabs, so we cannot call them from backend_init. */
>> - init_set_costs ();
>> - ira_init ();
>> -
>> - expand_dummy_function_end ();
>> + {
>> + backend_init_target ();
>> + this_target_rtl->target_specific_initialized = true;
>> + }
>> }
>>
>> /* Language-dependent initialization. Returns nonzero on success. */
