From: Richard Sandiford <richard.sandiford@arm.com>
To: gcc-patches@gcc.gnu.org
Subject: [PATCH 5/8] aarch64: Tweak the cost of elementwise stores
Date: Tue, 03 Aug 2021 13:05:43 +0100 [thread overview]
Message-ID: <mpttuk6bunc.fsf@arm.com> (raw)
In-Reply-To: <mptlf5id9bw.fsf@arm.com> (Richard Sandiford's message of "Tue, 03 Aug 2021 13:03:15 +0100")
When the vectoriser scalarises a strided store, it counts one
scalar_store for each element plus one vec_to_scalar extraction
for each element. However, extracting element 0 is free on AArch64,
so it should have zero cost.
I don't have a testcase that requires this for existing -mtune
options, but it becomes more important with a later patch.
gcc/
* config/aarch64/aarch64.c (aarch64_is_store_elt_extraction): New
function, split out from...
(aarch64_detect_vector_stmt_subtype): ...here.
(aarch64_add_stmt_cost): Treat extracting element 0 as free.
---
gcc/config/aarch64/aarch64.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 36f11808916..084f8caa0da 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -14622,6 +14622,18 @@ aarch64_builtin_vectorization_cost (enum vect_cost_for_stmt type_of_cost,
}
}
+/* Return true if an operaton of kind KIND for STMT_INFO represents
+ the extraction of an element from a vector in preparation for
+ storing the element to memory. */
+static bool
+aarch64_is_store_elt_extraction (vect_cost_for_stmt kind,
+ stmt_vec_info stmt_info)
+{
+ return (kind == vec_to_scalar
+ && STMT_VINFO_DATA_REF (stmt_info)
+ && DR_IS_WRITE (STMT_VINFO_DATA_REF (stmt_info)));
+}
+
/* Return true if STMT_INFO represents part of a reduction. */
static bool
aarch64_is_reduction (stmt_vec_info stmt_info)
@@ -14959,9 +14971,7 @@ aarch64_detect_vector_stmt_subtype (vec_info *vinfo, vect_cost_for_stmt kind,
/* Detect cases in which vec_to_scalar is describing the extraction of a
vector element in preparation for a scalar store. The store itself is
costed separately. */
- if (kind == vec_to_scalar
- && STMT_VINFO_DATA_REF (stmt_info)
- && DR_IS_WRITE (STMT_VINFO_DATA_REF (stmt_info)))
+ if (aarch64_is_store_elt_extraction (kind, stmt_info))
return simd_costs->store_elt_extra_cost;
/* Detect SVE gather loads, which are costed as a single scalar_load
@@ -15382,6 +15392,12 @@ aarch64_add_stmt_cost (class vec_info *vinfo, void *data, int count,
if (vectype && aarch64_sve_only_stmt_p (stmt_info, vectype))
costs->saw_sve_only_op = true;
+ /* If we scalarize a strided store, the vectorizer costs one
+ vec_to_scalar for each element. However, we can store the first
+ element using an FP store without a separate extract step. */
+ if (aarch64_is_store_elt_extraction (kind, stmt_info))
+ count -= 1;
+
stmt_cost = aarch64_detect_scalar_stmt_subtype
(vinfo, kind, stmt_info, stmt_cost);
next prev parent reply other threads:[~2021-08-03 12:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-03 12:03 [PATCH 0/8] aarch64 vector cost tweaks Richard Sandiford
2021-08-03 12:03 ` [PATCH 1/8] aarch64: Turn sve_width tuning field into a bitmask Richard Sandiford
2021-08-03 12:04 ` [PATCH 2/8] aarch64: Add a simple fixed-point class for costing Richard Sandiford
2021-08-03 12:04 ` [PATCH 3/8] aarch64: Split out aarch64_adjust_body_cost_sve Richard Sandiford
2021-08-03 12:05 ` [PATCH 4/8] aarch64: Add gather_load_xNN_cost tuning fields Richard Sandiford
2021-08-03 12:05 ` Richard Sandiford [this message]
2021-08-04 11:43 ` [PATCH 5/8] aarch64: Tweak the cost of elementwise stores Richard Biener
2021-08-05 12:04 ` [PATCH] vect: Move costing helpers from aarch64 code Richard Sandiford
2021-08-05 12:11 ` Richard Biener
2021-08-05 13:06 ` Richard Sandiford
2021-08-03 12:06 ` [PATCH 6/8] aarch64: Tweak MLA vector costs Richard Sandiford
2021-08-04 11:45 ` Richard Biener
2021-08-04 12:14 ` Richard Sandiford
2021-08-04 12:19 ` Richard Sandiford
2021-08-03 12:06 ` [PATCH 7/8] aarch64: Restrict issue heuristics to inner vector loop Richard Sandiford
2021-08-03 12:06 ` [PATCH 8/8] aarch64: Add -mtune=neoverse-512tvb Richard Sandiford
2021-08-17 14:37 ` Richard Sandiford
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