From: Alexandre Oliva <aoliva@redhat.com>
To: Richard Henderson <rth@redhat.com>,
bernds_cb1@t-online.de (Bernd Schmidt)
Cc: gcc@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: [RFC] avoiding too narrow register classes in reload
Date: Tue, 14 Dec 2004 21:20:00 -0000 [thread overview]
Message-ID: <ork6rktw51.fsf@livre.redhat.lsd.ic.unicamp.br> (raw)
In-Reply-To: <20041214020635.GA16249@redhat.com>
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On Dec 14, 2004, Richard Henderson <rth@redhat.com> wrote:
> On Mon, Dec 13, 2004 at 07:20:21PM -0200, Alexandre Oliva wrote:
>> Does this look like a reasonable approach?
> Yes.
>> Should other locations that compare
>> reg_class_size with 1 be adjusted similarly?
> Probably would be good.
Here's the patch I've bootstrapped and tested on x86_64-linux-gnu.
There's one use of reg_class_size that I wasn't sure whether to
replace with the new macro, in combine_reloads():
rld[output_reload].out))))
&& ! reload_inner_reg_of_subreg (rld[i].in, rld[i].inmode,
rld[i].when_needed != RELOAD_FOR_INPUT)
&& (reg_class_size[(int) rld[i].class] || SMALL_REGISTER_CLASSES)
/* We will allow making things slightly worse by combining an
input and an output, but no worse than that. */
&& (rld[i].when_needed == RELOAD_FOR_INPUT
The logic was different from all other cases, that tested for
reg_class_size[...] == 1 || SMALL_REGISTER_CLASSES, and I couldn't
tell whether it was on purpose or a typo. Can anyone?
I realize the patch introduces some possibly-significant semantic
changes, in that NO_REGS is now regarded as a SMALL_REGISTER_CLASS_P
and so it passes a number of cases where we tested for
reg_class_size[...] == 1 || SMALL_REGISTER_CLASSES. Since
SMALL_REGISTER_CLASSES would pass, I figured this couldn't be a
problem. The last hunk, where || SMALL_REGISTER_CLASSES wasn't
present, uses the new predicate but also ensures that reg_class_size
is non-zero (it broke otherwise). Does it make sense to narrow the
predicate to hold only for non-empty classes, and adjust the
one-before-last hunk, that uses the negated predicate in a way that
requires it to hold for empty classes?
Ok to install this for now?
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Index: gcc/ChangeLog
from Alexandre Oliva <aoliva@redhat.com>
* reload.c (SMALL_REGISTER_CLASS_P): New.
(push_secondary_reload, find_reusable_reload, find_reloads): Use
it instead of testing only the class size.
Index: gcc/reload.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/reload.c,v
retrieving revision 1.260
diff -u -p -r1.260 reload.c
--- gcc/reload.c 7 Dec 2004 01:14:40 -0000 1.260
+++ gcc/reload.c 14 Dec 2004 21:16:57 -0000
@@ -113,6 +113,12 @@ a register with any other reload. */
(CONSTANT_P (X) \
&& GET_CODE (X) != HIGH \
&& !targetm.cannot_force_const_mem (X))
+
+/* True if C is a register class that has too few registers to be
+ safely used as a reload target class. */
+#define SMALL_REGISTER_CLASS_P(C) \
+ (reg_class_size [(int)(C)] <= 1 || CLASS_LIKELY_SPILLED_P (C))
+
\f
/* All reloads of the current insn are recorded here. See reload.h for
comments. */
@@ -443,7 +449,7 @@ push_secondary_reload (int in_p, rtx x,
== CODE_FOR_nothing))
|| (! in_p &&(rld[t_reload].secondary_out_icode
== CODE_FOR_nothing)))
- && (reg_class_size[(int) t_class] == 1 || SMALL_REGISTER_CLASSES)
+ && (SMALL_REGISTER_CLASS_P (t_class) || SMALL_REGISTER_CLASSES)
&& MERGABLE_RELOADS (secondary_type,
rld[t_reload].when_needed,
opnum, rld[t_reload].opnum))
@@ -501,7 +507,7 @@ push_secondary_reload (int in_p, rtx x,
|| (! in_p && rld[s_reload].secondary_out_reload == t_reload))
&& ((in_p && rld[s_reload].secondary_in_icode == t_icode)
|| (! in_p && rld[s_reload].secondary_out_icode == t_icode))
- && (reg_class_size[(int) class] == 1 || SMALL_REGISTER_CLASSES)
+ && (SMALL_REGISTER_CLASS_P (class) || SMALL_REGISTER_CLASSES)
&& MERGABLE_RELOADS (secondary_type, rld[s_reload].when_needed,
opnum, rld[s_reload].opnum))
{
@@ -755,7 +761,7 @@ find_reusable_reload (rtx *p_in, rtx out
|| (out != 0 && MATCHES (rld[i].out, out)
&& (in == 0 || rld[i].in == 0 || MATCHES (rld[i].in, in))))
&& (rld[i].out == 0 || ! earlyclobber_operand_p (rld[i].out))
- && (reg_class_size[(int) class] == 1 || SMALL_REGISTER_CLASSES)
+ && (SMALL_REGISTER_CLASS_P (class) || SMALL_REGISTER_CLASSES)
&& MERGABLE_RELOADS (type, rld[i].when_needed, opnum, rld[i].opnum))
return i;
@@ -780,7 +786,7 @@ find_reusable_reload (rtx *p_in, rtx out
&& GET_RTX_CLASS (GET_CODE (in)) == RTX_AUTOINC
&& MATCHES (XEXP (in, 0), rld[i].in)))
&& (rld[i].out == 0 || ! earlyclobber_operand_p (rld[i].out))
- && (reg_class_size[(int) class] == 1 || SMALL_REGISTER_CLASSES)
+ && (SMALL_REGISTER_CLASS_P (class) || SMALL_REGISTER_CLASSES)
&& MERGABLE_RELOADS (type, rld[i].when_needed,
opnum, rld[i].opnum))
{
@@ -1768,8 +1774,7 @@ combine_reloads (void)
rld[output_reload].out))))
&& ! reload_inner_reg_of_subreg (rld[i].in, rld[i].inmode,
rld[i].when_needed != RELOAD_FOR_INPUT)
- && (reg_class_size[(int) rld[i].class]
- || SMALL_REGISTER_CLASSES)
+ && (reg_class_size[(int) rld[i].class] || SMALL_REGISTER_CLASSES)
/* We will allow making things slightly worse by combining an
input and an output, but no worse than that. */
&& (rld[i].when_needed == RELOAD_FOR_INPUT
@@ -3484,7 +3489,7 @@ find_reloads (rtx insn, int replace, int
if (! win && ! did_match
&& this_alternative[i] != (int) NO_REGS
&& GET_MODE_SIZE (operand_mode[i]) <= UNITS_PER_WORD
- && reg_class_size[(int) preferred_class[i]] > 1)
+ && ! SMALL_REGISTER_CLASS_P (preferred_class[i]))
{
if (! reg_class_subset_p (this_alternative[i],
preferred_class[i]))
@@ -3542,7 +3547,8 @@ find_reloads (rtx insn, int replace, int
{
/* If the output is in a single-reg class,
it's costly to reload it, so reload the input instead. */
- if (reg_class_size[this_alternative[i]] == 1
+ if (reg_class_size[this_alternative[i]] > 0
+ && SMALL_REGISTER_CLASS_P (this_alternative[i])
&& (REG_P (recog_data.operand[j])
|| GET_CODE (recog_data.operand[j]) == SUBREG))
{
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--
Alexandre Oliva http://www.ic.unicamp.br/~oliva/
Red Hat Compiler Engineer aoliva@{redhat.com, gcc.gnu.org}
Free Software Evangelist oliva@{lsd.ic.unicamp.br, gnu.org}
next prev parent reply other threads:[~2004-12-14 21:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-13 21:20 Alexandre Oliva
2004-12-14 2:06 ` Richard Henderson
2004-12-14 21:20 ` Alexandre Oliva [this message]
2004-12-14 22:31 ` Richard Henderson
2004-12-15 6:56 ` Alexandre Oliva
2004-12-15 8:09 ` Richard Henderson
2004-12-15 20:07 ` Alexandre Oliva
2004-12-16 14:14 ` Dave Korn
2004-12-14 16:22 ` Bernd Schmidt
2004-12-14 20:53 ` Alexandre Oliva
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