From f000cb8cbc58b23a91c84d47d69481904981a1d9 Mon Sep 17 00:00:00 2001
From: Kyrylo Tkachov <ktkachov@nvidia.com>
Date: Fri, 20 Sep 2024 05:11:39 -0700
Subject: [PATCH] aarch64: Set Armv9-A generic L1 cache line size to 64 bytes
I'd like to use a value of 64 bytes for the L1 cache size for Armv9-A
generic tuning.
As described in g:9a99559a478111f7fbeec29bd78344df7651c707 this value is used
to set the std::hardware_destructive_interference_size value which we want to
be not overly large when running concurrent applications on large core-count
systems.
The generic value for Armv8-A systems and the port baseline is 256 bytes
because that's what the A64FX CPU has, as set de-facto in
aarch64_override_options_internal.
But for Armv9-A CPUs as far as I know there isn't anything larger
than 64 bytes, so we should be able to use the smaller value here and reduce
the size of concurrent structs that use
std::hardware_destructive_interference_size to pad their fields.
Bootstrapped and tested on aarch64-none-linux-gnu.
Signed-off-by: Kyrylo Tkachov <ktkachov@nvidia.com>
* config/aarch64/tuning_models/generic_armv9_a.h
(generic_armv9a_prefetch_tune): Define.
(generic_armv9_a_tunings): Use the above.
---
gcc/config/aarch64/tuning_models/generic_armv9_a.h | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/gcc/config/aarch64/tuning_models/generic_armv9_a.h b/gcc/config/aarch64/tuning_models/generic_armv9_a.h
index 999985ed40f6..76b3e4c9cf73 100644
--- a/gcc/config/aarch64/tuning_models/generic_armv9_a.h
+++ b/gcc/config/aarch64/tuning_models/generic_armv9_a.h
@@ -207,6 +207,18 @@ static const struct cpu_vector_cost generic_armv9_a_vector_cost =
&generic_armv9_a_vec_issue_info /* issue_info */
};
+/* Generic prefetch settings (which disable prefetch). */
+static const cpu_prefetch_tune generic_armv9a_prefetch_tune =
+{
+ 0, /* num_slots */
+ -1, /* l1_cache_size */
+ 64, /* l1_cache_line_size */
+ -1, /* l2_cache_size */
+ true, /* prefetch_dynamic_strides */
+ -1, /* minimum_stride */
+ -1 /* default_opt_level */
+};
+
static const struct tune_params generic_armv9_a_tunings =
{
&cortexa76_extra_costs,
@@ -239,7 +251,7 @@ static const struct tune_params generic_armv9_a_tunings =
(AARCH64_EXTRA_TUNE_CHEAP_SHIFT_EXTEND
| AARCH64_EXTRA_TUNE_USE_NEW_VECTOR_COSTS
| AARCH64_EXTRA_TUNE_MATCHED_VECTOR_THROUGHPUT), /* tune_flags. */
- &generic_prefetch_tune,
+ &generic_armv9a_prefetch_tune,
AARCH64_LDP_STP_POLICY_ALWAYS, /* ldp_policy_model. */
AARCH64_LDP_STP_POLICY_ALWAYS /* stp_policy_model. */
};
--
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