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

[Kito Cheng <kito dot cheng at gmail dot com>]

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 :)



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

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	\
-- 
1.9.3