From: Christophe Lyon <christophe.lyon@linaro.org>
To: "Andre Vieira (lists)" <Andre.SimoesDiasVieira@arm.com>
Cc: Ramana Radhakrishnan <ramana.gcc@googlemail.com>,
Bernd Schmidt <bschmidt@redhat.com>,
GCC Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] PR78255: Make postreload aware of NO_FUNCTION_CSE
Date: Mon, 12 Dec 2016 09:05:00 -0000 [thread overview]
Message-ID: <CAKdteOa4FORnw=Yr=OzfsTxPdnNKygv67uf2c9i-wgMg7k8fow@mail.gmail.com> (raw)
In-Reply-To: <584AD8E9.3000406@arm.com>
Hi Andre,
On 9 December 2016 at 17:16, Andre Vieira (lists)
<Andre.SimoesDiasVieira@arm.com> wrote:
> On 09/12/16 16:02, Ramana Radhakrishnan wrote:
>> On Fri, Dec 9, 2016 at 3:58 PM, Bernd Schmidt <bschmidt@redhat.com> wrote:
>>> On 12/09/2016 04:34 PM, Andre Vieira (lists) wrote:
>>>
>>>> Regardless, the other testcases I add in this patch show a sub-optimal
>>>> transformation done by postreload, turning direct calls into indirect
>>>> calls, for targets which have specifically pointed out that no CSE
>>>> should be done on functions through 'NO_FUNCTION_CSE'.
>>>
>>>
>>> What I'm wondering about is whether the patch wouldn't also prevent the
>>> opposite transformation. Is there a reason not to do that one? Can the
>>> problem be modeled by tweaking costs?
>>
>> I really don't think we should have a solution that relies on costs
>> for correctness .
>>
>> regards
>> Ramana
>>
>
> Regardless, 'reload_cse_simplify' would never perform the opposite
> transformation. It checks whether it can replace anything within the
> first argument INSN, with the second argument TESTREG. As the name
> implies this will always be a register. I double checked, the function
> is only called in 'reload_cse_regs' and 'testreg' is created using
> 'gen_rtx_REG'.
>
The new test (gcc.target/arm/pr78255-2.c scan-assembler b\\s+bar)
added at r243494 fails on old arm architectures, such as:
* arm-none-linux-gnueabi, forcing -march=armv5t in runtestflags
* arm-none-eabi with default cpu/fpu/mode
Christophe
> Cheers,
> Andre
next prev parent reply other threads:[~2016-12-12 9:05 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-09 14:03 Andre Vieira (lists)
2016-12-09 15:02 ` Bernd Schmidt
2016-12-09 15:34 ` Andre Vieira (lists)
2016-12-09 15:58 ` Bernd Schmidt
2016-12-09 16:02 ` Ramana Radhakrishnan
2016-12-09 16:16 ` Andre Vieira (lists)
2016-12-09 16:31 ` Bernd Schmidt
2016-12-09 17:22 ` [arm-embedded][committed] " Andre Vieira (lists)
2017-01-06 10:53 ` [PATCH] " Andre Vieira (lists)
2017-01-06 15:47 ` Jeff Law
2017-01-11 15:09 ` Andre Vieira (lists)
2016-12-12 9:05 ` Christophe Lyon [this message]
2016-12-20 16:48 ` [ARM][committed] Fix for PR78255-2.c testism for targets that do not optimize for tailcall Andre Vieira (lists)
2016-12-09 16:01 ` [PATCH] PR78255: Make postreload aware of NO_FUNCTION_CSE Jeff Law
2016-12-09 15:47 Wilco Dijkstra
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