| Message ID | mpttuk6bunc.fsf@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | aarch64 vector cost tweaks | expand |
On Tue, Aug 3, 2021 at 2:09 PM Richard Sandiford via Gcc-patches <gcc-patches@gcc.gnu.org> wrote: > > 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))); > +} It would be nice to put functions like this in tree-vectorizer.h in some section marked with a comment to contain helpers for the target add_stmt_cost. > /* 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); >
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);