Re: [PATCH][ARM] PR target/70008

[Michael Collison <michael dot collison at linaro dot org>]

On 2/29/2016 4:06 AM, Kyrill Tkachov wrote:
> Hi Michael,
>
> On 29/02/16 04:47, Michael Collison wrote:
> > This patches address PR 70008, where a reverse subtract with carry 
> > instruction can be generated in thumb2 mode. It was tested with no 
> > regressions in arm and thumb modes on the following targets:
> >
> > arm-none-linux-gnueabi
> > arm-none-linux-gnuabihf
> > armeb-none-linux-gnuabihf
> > arm-none-eabi
> >
> > Okay for trunk?
> >
> > 2016-02-28  Michael Collison <michael.collison@linaro.org>
> >
> >     PR target/70008
> >     * config/arm/arm.md (*subsi3_carryin): Only match pattern if
> >     TARGET_ARM due to 'rsc' instruction alternative.
> >     * config/arm/thumb2.md (*thumb2_subsi3_carryin): New pattern.
>
> The *subsi3_carrying pattern has the arch attribute:
>    (set_attr "arch" "*,a")
>
> That means that the second alternative that generates the RSC 
> instruction is only enabled
> for ARM mode. Do you have a testcase where this doesn't happen and 
> this pattern generates
> the second alternative for Thumb2?

No I don't have a test case; i noticed the pattern when working on the 
overflow project. I did not realize
that an attribute could affect the matching of an alternative. I will 
close the bug.

> Thanks,
> Kyrill