Re: [Patch][ARM] Add -mbranch-cost option, and update a few tests

[Rainer Orth <ro at CeBiTec dot Uni-Bielefeld dot DE>]

Hi Christophe,

> On 10 January 2018 at 15:44, Jakub Jelinek <jakub@redhat.com> wrote:
>> On Mon, Oct 23, 2017 at 02:30:24PM +0200, Christophe Lyon wrote:
>>> After Jakub's suggestion in PR82120 and PR81184, the attached patch
>>> adds the -mbranch-cost option to the ARM target. My understanding
>>> is that it's intended to be used internally for testing and does not
>>> require user-facing documentation.
>>>
>>> I have updated a few tests, validation on aarch64 & arm targets shows
>>> no regression,
>>> and a few improvements when targeting cortex-a5 or cortex-m3:
>>> gcc.dg/tree-ssa/reassoc-3[3456].c now pass.
>>>
>>> That being said, I'm not sure about the other targets for which I
>>> changed the condition,
>>> and I am also concerned by the fact that it has no impact on
>>> gcc.dg/pr21643.c and gcc.dg/tree-ssa/phi-opt-11.c (PR81184).
>>>
>>> Should I restrict my patch to the only tests where it has an impact
>>> (gcc.dg/tree-ssa/reassoc-3[3456].c) ?
>>
>> Let's change all and watch the effects on all targets in testresults,
>> we can fine tune later on.
>>
> OK, thanks
>
>> Does pr21643.c really fail somewhere on arm*?  Tried -mcpu=cortex-a5
>> and don't see the failure in x86_64-linux -> armv7a-hardfloat-linux-gnueabi
>> cross.
>
> Yes, for me still fails on arm-none-linux-gnueabihf
> --with-cpu=cortex-a5 --with-fpu=vfpv3-d16-fp16
>
>>
>>> gcc/ChangeLog:
>>>
>>> 2017-10-23  Christophe Lyon  <christophe.lyon@linaro.org>
>>>
>>>       * config/arm/arm.opt (-mbranch-cost): New option.
>>>       * config/arm/arm.h (BRANCH_COST): Take arm_branch_cost into
>>>       account.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> 2017-10-23  Christophe Lyon  <christophe.lyon@linaro.org>
>>>
>>>       * lib/target-supports.exp (check_effective_target_branch_cost):
>>>       New function.
>>>       * gcc.dg/builtin-bswap-7.c: Use branch_cost effective target.
>>>       * gcc.dg/pr21643.c: Likewise.
>>>       * gcc.dg/pr46309.c: Likewise.
>>>       * gcc.dg/tree-ssa/phi-opt-11.c: Likewise.
>>>       * gcc.dg/tree-ssa/phi-opt-2.c: Likewise.
>>>       * gcc.dg/tree-ssa/reassoc-32.c: Likewise.
>>>       * gcc.dg/tree-ssa/reassoc-33.c: Likewise.
>>>       * gcc.dg/tree-ssa/reassoc-34.c: Likewise.
>>>       * gcc.dg/tree-ssa/reassoc-35.c: Likewise.
>>>       * gcc.dg/tree-ssa/reassoc-36.c: Likewise.
>>>       * gcc.dg/tree-ssa/ssa-ifcombine-13.c: Likewise.
>>>       * gcc.dg/tree-ssa/ssa-ifcombine-ccmp-1.c: Likewise.
>>>       * gcc.dg/tree-ssa/ssa-ifcombine-ccmp-2.c: Likewise.
>>>       * gcc.dg/tree-ssa/ssa-ifcombine-ccmp-3.c: Likewise.
>>>       * gcc.dg/tree-ssa/ssa-ifcombine-ccmp-4.c: Likewise.
>>>       * gcc.dg/tree-ssa/ssa-ifcombine-ccmp-5.c: Likewise.
>>>       * gcc.dg/tree-ssa/ssa-ifcombine-ccmp-6.c: Likewise.
>>
>> Ok for trunk.
>>
>> Note, unreviewed patches should be pinged from time to time.
> Sorry, I thought the patch was too crappy ;-)

not at all, but it has two problems:

* The new branch_cost effective-target keyword needs documenting in
  sourcebuild.texi, as always.

* The patch caused a regression on non-Linux x86 targets:

FAIL: gcc.dg/tree-ssa/phi-opt-2.c scan-tree-dump-times optimized "if" 1 (found 0 times)

  I'm seeing this on i386-pc-solaris2.*, and according to
  gcc-testresults it happens on *86-*-freebsd*, too.  The reason is
  simple: while the original testcase enabled -mbranch-cost for all
  i?86-*-* and x86_64-*-* targets, the new branch_cost keyword does so
  only for i?86-*-linux* and x86_64-*-linux* for no reason I can see.
  Fixing that lets the test PASS on Solaris/x86, too, so I'm installing
  the following patch.

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University


2018-01-11  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	* lib/target-supports.exp (check_effective_target_branch_cost):
	Accept all x86 targets.

# HG changeset patch
# Parent  76d1f957bcf2be744c67e2ff4587f00e87722cc9
Include all x86 targets in branch_cost effective target

diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -8623,7 +8623,7 @@ proc check_effective_target_branch_cost 
 	 || [istarget avr*-*-*]
 	 || [istarget epiphany*-*-*]
 	 || [istarget frv*-*-*]
-	 || [istarget i?86-*-linux*] || [istarget x86_64-*-linux*]
+	 || [istarget i?86-*-*] || [istarget x86_64-*-*]
 	 || [istarget mips*-*-*]
 	 || [istarget s390*-*-*]
 	 || [istarget riscv*-*-*]