On 01/22/2018 06:46 AM, Luis Machado wrote:
> The following patch adds an option to control software prefetching of memory
> references with non-constant/unknown strides.
>
> Currently we prefetch these references if the pass thinks there is benefit to
> doing so. But, since this is all based on heuristics, it's not always the case
> that we end up with better performance.
>
> For Falkor there is also the problem of conflicts with the hardware
> prefetcher,
> so we need to be more conservative in terms of what we issue software prefetch
> hints for.
>
> This also aligns GCC with what LLVM does for Falkor.
>
> Similarly to the previous patch, the defaults guarantee no change in behavior
> for other targets and architectures.
>
> I've regression-tested and bootstrapped it on aarch64-linux. No problems
> found.
>
> Ok?
>
> 2018-01-22 Luis Machado <luis.mach...@linaro.org>
>
> Introduce option to control whether the software prefetch pass should
> issue prefetch hints for non-constant strides.
>
> gcc/
> * config/aarch64/aarch64-protos.h (cpu_prefetch_tune)
> <prefetch_dynamic_strides>: New const unsigned int field.
> * config/aarch64/aarch64.c (generic_prefetch_tune): Update to include
> prefetch_dynamic_strides.
> (exynosm1_prefetch_tune): Likewise.
> (thunderxt88_prefetch_tune): Likewise.
> (thunderx_prefetch_tune): Likewise.
> (thunderx2t99_prefetch_tune): Likewise.
> (qdf24xx_prefetch_tune): Likewise. Set prefetch_dynamic_strides to 0.
> (aarch64_override_options_internal): Update to set
> PARAM_PREFETCH_DYNAMIC_STRIDES.
> * doc/invoke.texi (prefetch-dynamic-strides): Document new option.
> * params.def (PARAM_PREFETCH_DYNAMIC_STRIDES): New.
> * params.h (PARAM_PREFETCH_DYNAMIC_STRIDES): Define.
> * tree-ssa-loop-prefetch.c (should_issue_prefetch_p): Account for
> prefetch-dynamic-strides setting.
OK for the trunk.
jeff
