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| author | Luis Machado <luis.machado@linaro.org> | 2018-05-23 16:23:11 +0000 |
|---|---|---|
| committer | Luis Machado <luisgpm@gcc.gnu.org> | 2018-05-23 16:23:11 +0000 |
| commit | d2ff35c0913539a31782fbc05bb6d4c2ce74f2ce (patch) | |
| tree | 36f27cdd1a5fcc65a32d45f16e798bdd393b5cb3 /gcc/tree-ssa-loop-prefetch.c | |
| parent | 59100dfc42bbe92caff61bca1560da4a30f99906 (diff) | |
[Patch 02/02] Introduce prefetch-dynamic-strides option
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.
gcc/ChangeLog:
2018-05-23 Luis Machado <luis.machado@linaro.org>
* config/aarch64/aarch64-protos.h (cpu_prefetch_tune)
<prefetch_dynamic_strides>: New const bool 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
false.
(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.
From-SVN: r260618
Diffstat (limited to 'gcc/tree-ssa-loop-prefetch.c')
| -rw-r--r-- | gcc/tree-ssa-loop-prefetch.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/gcc/tree-ssa-loop-prefetch.c b/gcc/tree-ssa-loop-prefetch.c index ac89bf76a6a..c3e7fd1e529 100644 --- a/gcc/tree-ssa-loop-prefetch.c +++ b/gcc/tree-ssa-loop-prefetch.c @@ -992,6 +992,16 @@ prune_by_reuse (struct mem_ref_group *groups) static bool should_issue_prefetch_p (struct mem_ref *ref) { + /* Do we want to issue prefetches for non-constant strides? */ + if (!cst_and_fits_in_hwi (ref->group->step) && PREFETCH_DYNAMIC_STRIDES == 0) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "Skipping non-constant step for reference %u:%u\n", + ref->group->uid, ref->uid); + return false; + } + /* Some processors may have a hardware prefetcher that may conflict with prefetch hints for a range of strides. Make sure we don't issue prefetches for such cases if the stride is within this particular |