This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

Re: [PATCH][ARM] Restrict MAX_CONDITIONAL_EXECUTE when -mrestrict-it is in place

From: Ramana Radhakrishnan <ramana dot radhakrishnan at foss dot arm dot com>
To: Kyrill Tkachov <kyrylo dot tkachov at foss dot arm dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
Cc: Richard Earnshaw <Richard dot Earnshaw at arm dot com>
Date: Thu, 11 Jun 2015 10:55:10 +0100
Subject: Re: [PATCH][ARM] Restrict MAX_CONDITIONAL_EXECUTE when -mrestrict-it is in place
Authentication-results: sourceware.org; auth=none
References: <5559BE41 dot 8040909 at foss dot arm dot com>



On 18/05/15 11:26, Kyrill Tkachov wrote:

Hi all,

When using the short Thumb2 IT blocks we want to also restrict ifcvt so that it will not end up generating a number of back-to-back cond_execs
that will later end up being back to back single-instruction IT blocks. Branching over them should be a better choice.

This patch implements that by setting max_insns_skipped to 1 when arm_restrict_it.

With this patch, I've seen GCC replace a number of sequences in places like SPEC2006 from:
      it    eq
      moveq    r1, r5
      it    ne
      movne    r1, r10
      it    eq
      moveq    r8, r4

to a branch over them.

Bootstrapped and tested on arm.
Ok for trunk?

Are you sure TREE_TARGET_THUMB2 is still valid in the code base afterChristian's latest round of ARM / Thumb patches ?



Ramana


Thanks,
Kyrill

2015-05-18  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

      * config/arm/arm.c (arm_option_params_internal): When optimising
      for speed set max_insns_skipped when arm_restrict_it.

2015-05-18  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

      * gcc.target/arm/short-it-ifcvt-1.c: New test.
      * gcc.target/arm/short-it-ifcvt-2.c: Likewise.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]