Re: [PATCH 2/3] LoongArch: Fix instruction costs [PR112936]

[chenglulu <chenglulu@loongson.cn>]

在 2023/12/15 下午3:56, chenglulu 写道:
>
> 在 2023/12/14 上午9:16, chenglulu 写道:
>>
>> 在 2023/12/13 下午9:20, Xi Ruoyao 写道:
>>> On Wed, 2023-12-13 at 20:22 +0800, chenglulu wrote:
>>>
>>> 在 2023/12/10 上午1:03, Xi Ruoyao 写道:
>>> Replace the instruction costs in loongarch_rtx_cost_data constructor
>>> based on micro-benchmark results on LA464 and LA664.
>>>
>>> This allows optimizations like "x * 17" to alsl, and "x * 68" to alsl
>>> and slli.
>>>
>>> gcc/ChangeLog:
>>>
>>>       PR target/112936
>>>       * config/loongarch/loongarch-def.cc
>>>       (loongarch_rtx_cost_data::loongarch_rtx_cost_data): Update
>>>       instruction costs per micro-benchmark results.
>>>       (loongarch_rtx_cost_optimize_size): Set all instruction costs
>>>       to (COSTS_N_INSNS (1) + 1).
>>>       * config/loongarch/loongarch.cc (loongarch_rtx_costs): Remove
>>>       special case for multiplication when optimizing for size.
>>>       Adjust division cost when TARGET_64BIT && !TARGET_DIV32.
>>>       Account the extra cost when TARGET_CHECK_ZERO_DIV and
>>>       optimizing for speed.
>>>
>>> gcc/testsuite/ChangeLog
>>>
>>>       PR target/112936
>>>       * gcc.target/loongarch/mul-const-reduction.c: New test.
>>> ---
>>>     gcc/config/loongarch/loongarch-def.cc         | 39 
>>> ++++++++++---------
>>>     gcc/config/loongarch/loongarch.cc             | 22 +++++------
>>>     .../loongarch/mul-const-reduction.c           | 11 ++++++
>>>     3 files changed, 43 insertions(+), 29 deletions(-)
>>>     create mode 100644 
>>> gcc/testsuite/gcc.target/loongarch/mul-const-reduction.c
>>>
>>> Well, I'm curious about how the value of this cost is obtained.
>>>
>>> I just make a loop containing 1000 mul.w instructions, then run the 
>>> loop
>>> 1000000 times and compare the time usage with running another loop
>>> containing 1000 addi.w instructions iterated 1000000 times too.
>>> Likewise for other instructions...
>>>
>> Ok. I need to do a performance comparison of the spec here. Probably 
>> tomorrow the results will be available.
>>
>> Thanks!
>>
> Sorry, there is a problem with my test environment, so the results may 
> not be available until tomorrow.

The SPEC2006 test was without problems, and the 483 had a 2.7 percent 
performance improvement.

Thanks!