[PATCH][AArch64] LR register not used in leaf functions

[Kugan]

On 23/09/14 01:58, Jiong Wang wrote:
> On 22/09/14 16:43, Kugan wrote:
> 
>> AArch64 has the same issue ARM had where the LR register was not used in
>> leaf functions. This was reported in
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42017. In AArch64, this
>> test-case need to be added with more live ranges for the need for the
>> LR_REGNUM. i.e test-case in the PR needs additional loops up to r31 for
>> the case AArch64 to see this.
>>
>> The same fix (from the thread
>> https://gcc.gnu.org/ml/gcc-patches/2011-04/msg02191.html) which went
>> into ARM should apply to AArch64 as well. Regression tested on qemu for
>> aarch64-none-linux-gnu with no new regressions. Is this OK for trunk?
> This still be a partial fix. LR should be a caller-saved register free
> to use in case it's saved properly to across function call.

Indeed. This should be improved from the generic code. Right now, if a
hard register is used in EPILOGUE_USES, it conflicts with all the live
ranges till a call site kills.  I think we should have this patch till
the generic code can be improved.

Thanks,
Kugan

> 
> I had a very similar patch to this sitting in my local tree and under
> various benchmark analysis.
> 
> -- Jiong
>>
>> Thanks,
>> Kugan
>>
>>
>> gcc/ChangeLog:
>>
>> 2014-09-23  Kugan Vivekanandarajah  <kuganv@linaro.org>
>>
>>     * config/aarch64/aarch64.h (EPILOGUE_USES): Return true only after
>>     epilogue_completed is true.
>>
> 
>