From: Denis Chertykov <chertykov@gmail.com>
To: Georg-Johann Lay <avr@gjlay.de>
Cc: gcc-patches@gcc.gnu.org, Anatoly Sokolov <aesok@post.ru>,
"Eric B. Weddington" <eric.weddington@atmel.com>
Subject: Re: [Patch, AVR]: Fix PR46779
Date: Thu, 09 Jun 2011 19:51:00 -0000 [thread overview]
Message-ID: <BANLkTi=VAo8UcLDsvBp5vWk3qaO5RQvAKg@mail.gmail.com> (raw)
In-Reply-To: <4DF11D20.4030907@gjlay.de>
2011/6/9 Georg-Johann Lay <avr@gjlay.de>:
> Denis Chertykov schrieb:
>> 2011/6/9 Georg-Johann Lay <avr@gjlay.de>:
>>> This is a tentative patch to fix PR46779 and hopefully also related
>>> issues like PR45291.
>>>
>> - /* Disallow QImode in stack pointer regs. */
>> - if ((regno == REG_SP || regno == (REG_SP + 1)) && mode == QImode)
>> + /* Don't allocate data to non-GENERAL_REGS registers. */
>> +
>> + if (regno >= 32)
>> return 0;
>>
>> I think that we not need in this code.
>> GCC core must bother about this.
>
> I am unsure about that. There is the "q" constraint that is used for
> SP. register_operand will accept SP because regno_reg_class does not
> return NO_REGS for SP. So something must stop the register allocator
> from allocating ordinary data to SP.
I know, this is a FIXED_REGISTERS.
> In the current md there is "*movhi_sp" insn prior to "*movhi" insn.
> Besides that it is strongly discouraged to have more than one move
> insn for one mode, not each and every place looks at insn conditions.
I'm agree. May be better to rewrite it.
>
> Moreover, if there is an insn like
> (set (reg:HI 100)
> (reg:HI 101))
> that matches "*movhi", what will keep IRA from allocating one of the
> values to SP, i.e. chose alternative "q,r" or "r,q"?
FIXED_REGISTERS.
>> + {
>> + return 0;
>> + }
>>
>> Fragment from GCC info:
>> --------------------------------------
>> HARD_REGNO_MODE_OK (regno, mode)A C expression that is nonzero if it
>> is permissible to store a value of mode mode in hard register number
>> regno (or in several registers starting with that one). For a machine
>> where all registers are equivalent, a suitable definition is
>>
>> #define HARD_REGNO_MODE_OK(REGNO, MODE) 1
>>
>> You need not include code to check for the numbers of fixed registers,
>> because the allocation mechanism considers them to be always occupied.
>> -----------------------------------------
>> Again, GCC core must bother about this.
>
> I agree with you. However, I think that the risk of spill failure
> should be minimized. I have no idea how to fix a splill failure like
> the following that occurs in testsuite (with -Os, no matter if the
> patch is applied or not):
>
> ./gcc/testsuite/gcc.c-torture/execute/pr38051.c:189:1: error: unable
> to find a register to spill in class 'POINTER_REGS'
> ./gcc/testsuite/gcc.c-torture/execute/pr38051.c:189:1: error: this is
> the insn:
> (insn 61 60 62 10 (set (reg/v:SI 12 r12 [orig:73 b0 ] [73])
> (mem:SI (subreg:HI (reg/v:SI 70 [ srcp2 ]) 0) [2 *D.2218_56+0
> S4 A8])) ./gcc/testsuite/gcc.c-torture/execute/pr38051.c:64 12 {*movsi}
> (nil))
> ./gcc/testsuite/gcc.c-torture/execute/pr38051.c:189:1: internal
> compiler error: in spill_failure, at reload1.c:2113
>
> Actually I have no idea if the snip in avr_hard_regno_mode_ok actually
> would reduce the risk of spill failure :-/
I think, no.
I will try to debug reload for pr38051.c (It will be a long process 1-2 weeks)
Denis.
next prev parent reply other threads:[~2011-06-09 19:43 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-09 17:24 Georg-Johann Lay
2011-06-09 18:50 ` Denis Chertykov
2011-06-09 19:43 ` Georg-Johann Lay
2011-06-09 19:51 ` Denis Chertykov [this message]
2011-06-10 10:23 ` Georg-Johann Lay
2011-06-12 10:34 ` Denis Chertykov
2011-06-13 18:10 ` Georg-Johann Lay
2011-06-13 22:37 ` Denis Chertykov
2011-06-14 10:39 ` Georg-Johann Lay
2011-06-14 11:38 ` Denis Chertykov
2011-06-14 21:38 ` Georg-Johann Lay
2011-06-14 23:04 ` Richard Henderson
2011-06-15 17:58 ` Richard Henderson
2011-06-15 21:58 ` Georg-Johann Lay
2011-06-15 22:20 ` Richard Henderson
2011-06-16 3:46 ` Richard Henderson
2011-06-16 11:37 ` Denis Chertykov
2011-06-16 12:01 ` Denis Chertykov
2011-06-16 14:07 ` Richard Henderson
2011-06-16 18:18 ` Denis Chertykov
2011-06-16 18:57 ` Richard Henderson
2011-06-16 19:33 ` Denis Chertykov
2011-06-16 19:42 ` Richard Henderson
2011-06-16 20:04 ` Denis Chertykov
2011-06-16 14:36 ` Richard Henderson
2011-06-16 14:52 ` Bernd Schmidt
2011-06-16 15:13 ` Richard Henderson
2011-06-16 18:57 ` Denis Chertykov
2011-06-23 20:48 ` Denis Chertykov
2011-06-23 22:04 ` Richard Henderson
2011-06-26 20:03 ` Denis Chertykov
2011-06-26 20:51 ` Georg-Johann Lay
2011-06-27 8:41 ` Denis Chertykov
2011-06-27 9:19 ` Georg-Johann Lay
2011-06-27 10:17 ` Denis Chertykov
2011-07-07 9:59 ` Georg-Johann Lay
2011-07-07 18:21 ` Denis Chertykov
2011-07-08 10:12 ` Georg-Johann Lay
2011-07-08 10:25 ` Denis Chertykov
2011-07-08 12:16 ` Georg-Johann Lay
2011-06-22 3:28 ` Hans-Peter Nilsson
2011-06-22 17:03 ` Georg-Johann Lay
2011-06-23 12:51 ` Hans-Peter Nilsson
2011-06-23 13:00 ` Hans-Peter Nilsson
2011-06-09 20:03 ` Georg-Johann Lay
2011-06-10 9:27 ` Georg-Johann Lay
2011-06-21 17:17 ` Georg-Johann Lay
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='BANLkTi=VAo8UcLDsvBp5vWk3qaO5RQvAKg@mail.gmail.com' \
--to=chertykov@gmail.com \
--cc=aesok@post.ru \
--cc=avr@gjlay.de \
--cc=eric.weddington@atmel.com \
--cc=gcc-patches@gcc.gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).