ira.c update_equiv_regs patch causes gcc/testsuite/gcc.target/arm/pr43920-2.c regression

[Jeff Law]

On 04/20/2015 01:09 AM, Shiva Chen wrote:
> Hi, Jeff
>
> Thanks for your advice.
>
> can_replace_by.patch is the new patch to handle both cases.
>
> pr43920-2.c.244r.jump2.ori is the original  jump2 rtl dump
>
> pr43920-2.c.244r.jump2.patch_can_replace_by is the jump2 rtl dump
> after patch  can_replace_by.patch
>
> Could you help me to review the patch?
Thanks.  This looks pretty good.

I expanded the comment for the new function a bit and renamed the 
function in an effort to clarify its purpose.  From reviewing 
can_replace_by, it seems it should have been handling this case, but 
clearly wasn't due to implementation details.

I then bootstrapped and regression tested the patch on x86_64-linux-gnu 
where it passed.  I also instrumented that compiler to see how often 
this code triggers.  During a bootstrap it triggers a couple hundred 
times (which is obviously a proxy for cross jumping improvements).  So 
it's triggering regularly on x86_64, which is good.

I also verified that this fixes BZ64916 for an arm-non-eabi toolchain 
configured with --with-arch=armv7.

Installed on the trunk.  No new testcase as it's covered by existing tests.

Thanks,,
jeff