Re: [PATCH] Remove CALLER_SAVE_PROFITABLE since nobody use it now

[Richard Earnshaw <rearnsha at arm dot com>]

On 19/08/14 15:24, Kito Cheng wrote:
> Hi Richard:
>> Hmm, I'm not sure about this.  It might not be used at present, but on:
>> AArch64, with more call-clobbered registers than call-saved registers, I
>> would expect this ought to be a win.  The fact that it isn't on today
>> may say more about the way it works than the concept that it's the wrong
>> thing to do in principle.
> 
> In my view, calculate cost/profit should be done by register allocator instead
> of a target hook/marco is more reasonable since register allocator can
> have more globe view to it, and IRA do it now.
> 
> And as Joseph say, no code calling it, so I think it's time to remove it.
> thanks for your comment :)
> 
> 

Objection withdrawn.

R.

> 
> Hi Joseph:
> 
>> Nothing uses it - not just no targets defining it, but no code calling it.
>> If you have a use in future for a target hook doing something suggested by
>> the name of this macro, by all means add one - but there's no point at all
>> in keeping the macro until then.  (It should of course be poisoned in
>> system.h when removing it, as standard when removing target macros.)
> Thanks, I add poison for CALLER_SAVE_PROFITABLE to system.h,
>  updated patch attached.
> 
> thanks for your review :)
> 
> ChangLog
> 2014-08-19  Kito Cheng  <kito@0xlab.org>
> 
>         * system.h (CALLER_SAVE_PROFITABLE): Poison.
>         * doc/tm.texi.in (CALLER_SAVE_PROFITABLE): Remove.
>         * gcc/doc/tm.texi: Regenerate.
>         * gcc/regs.h (CALLER_SAVE_PROFITABLE): Remove.
> 
> On Tue, Aug 19, 2014 at 4:26 AM, Joseph S. Myers
> <joseph@codesourcery.com> wrote:
>> On Mon, 18 Aug 2014, Richard Earnshaw wrote:
>>
>>> Hmm, I'm not sure about this.  It might not be used at present, but on
>>> AArch64, with more call-clobbered registers than call-saved registers, I
>>> would expect this ought to be a win.  The fact that it isn't on today
>>> may say more about the way it works than the concept that it's the wrong
>>> thing to do in principle.
>>
>> Nothing uses it - not just no targets defining it, but no code calling it.
>> If you have a use in future for a target hook doing something suggested by
>> the name of this macro, by all means add one - but there's no point at all
>> in keeping the macro until then.  (It should of course be poisoned in
>> system.h when removing it, as standard when removing target macros.)
>>
>> --
>> Joseph S. Myers
>> joseph@codesourcery.com
>>
>> 0001-Remove-CALLER_SAVE_PROFITABLE-since-nobody-use-it-no.patch
>>
>>
>> From 6a99f77eb6785c8d471329bda4bc67885f35909a Mon Sep 17 00:00:00 2001
>> From: Kito Cheng <kito@0xlab.org>
>> Date: Tue, 19 Aug 2014 22:10:47 +0800
>> Subject: [PATCH] Remove CALLER_SAVE_PROFITABLE since nobody use it now.
>>
>> ---
>>  gcc/doc/tm.texi    | 10 ----------
>>  gcc/doc/tm.texi.in | 10 ----------
>>  gcc/regs.h         |  8 --------
>>  gcc/system.h       |  3 ++-
>>  4 files changed, 2 insertions(+), 29 deletions(-)
>>
>> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
>> index 9dd8d68..4d6492b 100644
>> --- a/gcc/doc/tm.texi
>> +++ b/gcc/doc/tm.texi
>> @@ -4528,16 +4528,6 @@ If you enable it, GCC can save registers around function calls.  This
>>  makes it possible to use call-clobbered registers to hold variables that
>>  must live across calls.
>>  
>> -@defmac CALLER_SAVE_PROFITABLE (@var{refs}, @var{calls})
>> -A C expression to determine whether it is worthwhile to consider placing
>> -a pseudo-register in a call-clobbered hard register and saving and
>> -restoring it around each function call.  The expression should be 1 when
>> -this is worth doing, and 0 otherwise.
>> -
>> -If you don't define this macro, a default is used which is good on most
>> -machines: @code{4 * @var{calls} < @var{refs}}.
>> -@end defmac
>> -
>>  @defmac HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs})
>>  A C expression specifying which mode is required for saving @var{nregs}
>>  of a pseudo-register in call-clobbered hard register @var{regno}.  If
>> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
>> index dd72b98..7a63353 100644
>> --- a/gcc/doc/tm.texi.in
>> +++ b/gcc/doc/tm.texi.in
>> @@ -3683,16 +3683,6 @@ If you enable it, GCC can save registers around function calls.  This
>>  makes it possible to use call-clobbered registers to hold variables that
>>  must live across calls.
>>  
>> -@defmac CALLER_SAVE_PROFITABLE (@var{refs}, @var{calls})
>> -A C expression to determine whether it is worthwhile to consider placing
>> -a pseudo-register in a call-clobbered hard register and saving and
>> -restoring it around each function call.  The expression should be 1 when
>> -this is worth doing, and 0 otherwise.
>> -
>> -If you don't define this macro, a default is used which is good on most
>> -machines: @code{4 * @var{calls} < @var{refs}}.
>> -@end defmac
>> -
>>  @defmac HARD_REGNO_CALLER_SAVE_MODE (@var{regno}, @var{nregs})
>>  A C expression specifying which mode is required for saving @var{nregs}
>>  of a pseudo-register in call-clobbered hard register @var{regno}.  If
>> diff --git a/gcc/regs.h b/gcc/regs.h
>> index be81db4..36e803d 100644
>> --- a/gcc/regs.h
>> +++ b/gcc/regs.h
>> @@ -214,14 +214,6 @@ extern short *reg_renumber;
>>  
>>  extern int caller_save_needed;
>>  
>> -/* Predicate to decide whether to give a hard reg to a pseudo which
>> -   is referenced REFS times and would need to be saved and restored
>> -   around a call CALLS times.  */
>> -
>> -#ifndef CALLER_SAVE_PROFITABLE
>> -#define CALLER_SAVE_PROFITABLE(REFS, CALLS)  (4 * (CALLS) < (REFS))
>> -#endif
>> -
>>  /* Select a register mode required for caller save of hard regno REGNO.  */
>>  #ifndef HARD_REGNO_CALLER_SAVE_MODE
>>  #define HARD_REGNO_CALLER_SAVE_MODE(REGNO, NREGS, MODE) \
>> diff --git a/gcc/system.h b/gcc/system.h
>> index 29da797..3f2cfa1 100644
>> --- a/gcc/system.h
>> +++ b/gcc/system.h
>> @@ -933,7 +933,8 @@ extern void fancy_abort (const char *, int, const char *) ATTRIBUTE_NORETURN;
>>  	CONST_DOUBLE_OK_FOR_LETTER_P EXTRA_CONSTRAINT			   \
>>  	REG_CLASS_FROM_CONSTRAINT REG_CLASS_FOR_CONSTRAINT		   \
>>  	EXTRA_CONSTRAINT_STR EXTRA_MEMORY_CONSTRAINT			   \
>> -	EXTRA_ADDRESS_CONSTRAINT CONST_DOUBLE_OK_FOR_CONSTRAINT_P
>> +	EXTRA_ADDRESS_CONSTRAINT CONST_DOUBLE_OK_FOR_CONSTRAINT_P	   \
>> +	CALLER_SAVE_PROFITABLE
>>  
>>  /* Hooks that are no longer used.  */
>>   #pragma GCC poison LANG_HOOKS_FUNCTION_MARK LANG_HOOKS_FUNCTION_FREE	\