Re: LRA patch for PR87718

[Sam Tebbs <Sam.Tebbs@arm.com>]

On 12/20/18 10:38 AM, Sam Tebbs wrote:
> On 11/24/18 11:29 AM, Christophe Lyon wrote:
>
>> On Thu, 22 Nov 2018 at 18:30, Vladimir Makarov <vmakarov@redhat.com>
>> wrote:
>>> The following patch fixes
>>>
>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87718
>>>
>>> The patch adds a special treatment for moves with a hard register in
>>> register cost and class calculation.
>>>
>>> The patch was bootstrapped and tested on x86-64 and ppc64.
>>>
>>> I found two testsuite regressions because of the patch. The expected
>>> generated code for PR82361 test is too specific. GCC with the patch
>>> generates the same quality code but with a different hard register on
>>> x86-64. So I just changed the test for PR82361.
>>>
>>> Another test is for ppc64. I think the expected generated code for
>>> this test is wrong. I'll submit a changed test for a discussion later.
>>>
>>> Although I spent much time on the solution and I think it is the
>>> right one, the patch is in very sensitive area of RA and may affect
>>> expected code generation for many targets. I am ready to work on the
>>> new regressions as soon as they are found.
>>>
>>> The patch was committed as rev. 260385.
>>>
>> Hi,
>>
>> This patch introduced at least several ICEs on arm targets:
>> on arm-none-linux-gnueabi --with-cpu=cortex-a9:
> <snip>
>> There are other regressions on the same targets, but not ICEs.
>> I can report them later.
>>
>> Thanks,
>>
>> Christophe
> Hi Christophe and Vladimir,
>
> Here are the regressions seen on arm-none-linux-gnueabihf and arm-none-eabi.
>
> FAIL: gcc.target/arm/armv8_2-fp16-move-1.c scan-assembler-times
> ldrh\\tr[0-9]+ 2
> FAIL: gcc.target/arm/armv8_2-fp16-move-1.c scan-assembler-times
> vld1\\.16\\t{d[0-9]+\\[[0-9]+\\]}, \\[r[0-9]+\\] 2
> FAIL: gcc.target/arm/armv8_2-fp16-move-1.c scan-assembler-times
> vmov\\.f16\\ts[0-9]+, r[0-9]+ 2
> FAIL: gcc.target/arm/fp16-aapcs-1.c scan-assembler
> vmov(\\.f16)?\\tr[0-9]+, s[0-9]+
> FAIL: gcc.target/arm/fp16-aapcs-1.c scan-assembler vmov(\\.f16)?\\ts0,
> r[0-9]+
> FAIL: gcc.target/arm/fp16-aapcs-3.c scan-assembler-times vmov\\tr[0-9]+,
> s[0-2] 2
> FAIL: gcc.target/arm/fp16-aapcs-3.c scan-assembler-times vmov\\ts0,
> r[0-9]+ 2
>
> I didn't see a bug report for these, so I will open one.
>
> It is not clear if the test cases should be adjusted because of your
> patch or if they are failing because of incorrect codegen. Attached is
> the code generated for armv8_2-fp16-move-1.c (one of the test files
> failing) with and without your patch.
>
> Full command line used to compile and test armv8_2-fp16-move-1.c:
>
> bin/gcc armv8_2-fp16-move-1.c -fno-diagnostics-show-caret
> -fno-diagnostics-show-line-numbers -fdiagnostics-color=never -O2
> -mfpu=fp-armv8 -march=armv8.2-a+fp16 -mfloat-abi=hard -ffat-lto-objects
> -fno-ident -S -o armv8_2-fp16-move-1.s.
Reported as PR 88560 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88560).