Re: [PATCH] amdgcn: Enable SIMD vectorization of math functions

[Andre Vieira (lists) via Gcc-patches]

On 01/03/2023 10:01, Andrew Stubbs wrote:
> On 28/02/2023 23:01, Kwok Cheung Yeung wrote:
>> Hello
>>
>> This patch implements the TARGET_VECTORIZE_BUILTIN_VECTORIZED_FUNCTION
>> target hook for the AMD GCN architecture, such that when vectorized,
>> calls to builtin standard math functions such as asinf, exp, pow etc.
>> are converted to calls to the recently added vectorized math functions
>> for GCN in Newlib. The -fno-math-errno flag is required in addition to
>> the usual vectorization optimization flags for this to occur, and some
>> of the math functions (the larger double-precision ones) require a
>> large stack size to function properly.
>>
>> This patch requires the GCN vector math functions in Newlib to
>> function - these were included in the recent 4.3.0.20230120 snapshot.
>> As this was a minimum requirement starting from the patch 'amdgcn,
>> libgomp: Manually allocated stacks', this should not be a problem.
>>
>> I have added new testcases in the testsuite that compare the output of
>> the vectorized math functions against the scalar, passing if they are
>> sufficiently close. With the testcase for standalone GCN (without
>> libgomp) in gcc.target/gcn/, there is a problem since gcn-run
>> currently cannot set the stack size correctly in DejaGnu testing, so I
>> have made it a compile test for now - it is still useful to check that
>> calls to the correct functions are being made. The runtime correctness
>> is still covered by the libgomp test.
>>
>> Okay for trunk?
>
> The main part of the patch is OK, with the small changes below.
>
> Others have pointed out that "omp declare simd" exists, but you and I
> have been all through that verbally, long ago, and as Tobias says the
> offload compiler cannot rely on markup in the host compiler's header
> files to solve this problem.

For what it's worth, I am currently working on enabling "omp declare 
simd" for SVE and more importantly teaching GCC to use "omp declare 
variant"'s with simd construct's as simdclones during autovect. This 
gives a bit more control on what simdclones you advertise as available. 
I hope to have some RFC's on here soon. I obviously am not familiar with 
your constraints but just wanted to let you know.