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Re: Update postreload.c to avoid long compilation time
- From: Martin Thuresson <martint at google dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: Bernd Schmidt <bernds at codesourcery dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 5 Aug 2010 15:11:31 -0700
- Subject: Re: Update postreload.c to avoid long compilation time
- References: <AANLkTi=UapBhS8xBT5LdOFn7YL_dOKJPVzu7S-NN0uBs@mail.gmail.com> <4C536839.email@example.com> <AANLkTi=njbubR5nWZvoheRbu0Htsvpz1vN6XO1GwMJyN@mail.gmail.com> <4C5B29C2.firstname.lastname@example.org>
On Thu, Aug 5, 2010 at 2:14 PM, Jeff Law <email@example.com> wrote:
> ?On 08/04/10 12:39, Martin Thuresson wrote:
>> On Fri, Jul 30, 2010 at 5:03 PM, Bernd Schmidt<firstname.lastname@example.org>
>>> On 07/31/2010 01:07 AM, Martin Thuresson wrote:
>>>> This patch updates the handling of temporary registers in postreload.c
>>>> to avoid very long build times in certain files.
>>>> By creating new registers instead of updating one existing one using
>>>> SET_REGNO it avoids going through the scan df structure.
>>>> Im new to gcc RTL and appreciate any feedback.
>>>> In the (inspired from real code) attached source, the time
>>>> for "reload CSE regs" went down from 20 usr seconds to less than 1.
>>> I have trouble reproducing the slowness. ?Which target are you using?
>> It seems that I did not include the larger testcase I had. I attached
>> it and these are the build times I measured:
>> Target: x86_64-unknown-linux-gnu
>> Options: ?-g -O2 -ftime-report -c
>> ?reload CSE regs ? ? ? : ?13.65 (81%) usr ? 0.01 (25%) sys ?13.73
>> (81%) wall ? ?2812 kB ( 4%) ggc
>> reload CSE regs ? ? ? : ? 0.16 ( 6%) usr ? 0.01 (14%) sys ? 0.17 ( 6%)
>> wall ? ?2812 kB ( 4%) ggc
>>> It's a bit unfortunate, and probably avoidable, to create additional
>>> garbage RTL. ?Maybe what's really needed is
>>> ?df_set_flags (DF_DEFER_INSN_RESCAN);
>>> at the top of postreload? ?Can you try that? ?Or, even simpler, avoid
>>> the SET_REGNO macro, and check all other occurrences of it. ?There seem
>>> to be a few, e.g. in caller-save.c or ira.c, which also probably
>>> shouldn't invoke df.
>> I updated the patch by introducing SET_REGNO_RAW and updated the
>> postreload.c, caller-save.c and ira.c.
>> I saw no new test failures.
> I was going to look at your patch, but you only included the SET_REGNO_RAW
> changes. ?It's customary to repost the entire patch after you update it to
> address issues from reviewers.
The included patch was the complete, as the comments I got simplified it.
I'm sorry if I missed something, and would be happy to try to address that.