[Vectorizer] Add SLP support for masked loads
Richard Sandiford
richard.sandiford@arm.com
Fri Apr 26 13:17:00 GMT 2019
Alejandro Martinez Vicente <Alejandro.MartinezVicente@arm.com> writes:
> Hi,
>
> Current vectorizer doesn't support masked loads for SLP. We should add that, to
> allow things like:
>
> void
> f (int *restrict x, int *restrict y, int *restrict z, int n)
> {
> for (int i = 0; i < n; i += 2)
> {
> x[i] = y[i] ? z[i] : 1;
> x[i + 1] = y[i + 1] ? z[i + 1] : 2;
> }
> }
>
> to be vectorized using contiguous loads rather than LD2 and ST2.
>
> This patch was motivated by SVE, but it is completely generic and should apply
> to any architecture with masked loads.
>
> After the patch is applied, the above code generates this output
> (-march=armv8.2-a+sve -O2 -ftree-vectorize):
>
> 0000000000000000 <f>:
> 0: 7100007f cmp w3, #0x0
> 4: 540002cd b.le 5c <f+0x5c>
> 8: 51000464 sub w4, w3, #0x1
> c: d2800003 mov x3, #0x0 // #0
> 10: 90000005 adrp x5, 0 <f>
> 14: 25d8e3e0 ptrue p0.d
> 18: 53017c84 lsr w4, w4, #1
> 1c: 910000a5 add x5, x5, #0x0
> 20: 11000484 add w4, w4, #0x1
> 24: 85c0e0a1 ld1rd {z1.d}, p0/z, [x5]
> 28: 2598e3e3 ptrue p3.s
> 2c: d37ff884 lsl x4, x4, #1
> 30: 25a41fe2 whilelo p2.s, xzr, x4
> 34: d503201f nop
> 38: a5434820 ld1w {z0.s}, p2/z, [x1, x3, lsl #2]
> 3c: 25808c11 cmpne p1.s, p3/z, z0.s, #0
> 40: 25808810 cmpne p0.s, p2/z, z0.s, #0
> 44: a5434040 ld1w {z0.s}, p0/z, [x2, x3, lsl #2]
> 48: 05a1c400 sel z0.s, p1, z0.s, z1.s
> 4c: e5434800 st1w {z0.s}, p2, [x0, x3, lsl #2]
> 50: 04b0e3e3 incw x3
> 54: 25a41c62 whilelo p2.s, x3, x4
> 58: 54ffff01 b.ne 38 <f+0x38> // b.any
> 5c: d65f03c0 ret
>
>
> I tested this patch in an aarch64 machine bootstrapping the compiler and
> running the checks.
>
> Alejandro
>
> gcc/Changelog:
>
> 2019-01-16 Alejandro Martinez <alejandro.martinezvicente@arm.com>
>
> * config/aarch64/aarch64-sve.md (copysign<mode>3): New define_expand.
> (xorsign<mode>3): Likewise.
> internal-fn.c: Marked mask_load_direct and mask_store_direct as
> vectorizable.
> tree-data-ref.c (data_ref_compare_tree): Fixed comment typo.
> tree-vect-data-refs.c (can_group_stmts_p): Allow masked loads to be
> combined even if masks different.
> (slp_vect_only_p): New function to detect masked loads that are only
> vectorizable using SLP.
> (vect_analyze_data_ref_accesses): Mark SLP only vectorizable groups.
> tree-vect-loop.c (vect_dissolve_slp_only_groups): New function to
> dissolve SLP-only vectorizable groups when SLP has been discarded.
> (vect_analyze_loop_2): Call vect_dissolve_slp_only_groups when needed.
> tree-vect-slp.c (vect_get_and_check_slp_defs): Check masked loads
> masks.
> (vect_build_slp_tree_1): Fixed comment typo.
> (vect_build_slp_tree_2): Include masks from masked loads in SLP tree.
> tree-vect-stmts.c (vect_get_vec_defs_for_operand): New function to get
> vec_defs for operand with optional SLP and vectype.
> (vectorizable_load): Allow vectorizaion of masked loads for SLP only.
> tree-vectorizer.h (_stmt_vec_info): Added flag for SLP-only
> vectorizable.
> tree-vectorizer.c (vec_info::new_stmt_vec_info): Likewise.
>
> gcc/testsuite/Changelog:
>
> 2019-01-16 Alejandro Martinez <alejandro.martinezvicente@arm.com>
>
> * gcc.target/aarch64/sve/mask_load_slp_1.c: New test for SLP
> vectorized masked loads.
>
> diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
> index 4f2ef45..67eee59 100644
> --- a/gcc/internal-fn.c
> +++ b/gcc/internal-fn.c
> @@ -100,11 +100,11 @@ init_internal_fns ()
> /* Create static initializers for the information returned by
> direct_internal_fn. */
> #define not_direct { -2, -2, false }
> -#define mask_load_direct { -1, 2, false }
> +#define mask_load_direct { -1, 2, true }
> #define load_lanes_direct { -1, -1, false }
> #define mask_load_lanes_direct { -1, -1, false }
> #define gather_load_direct { -1, -1, false }
> -#define mask_store_direct { 3, 2, false }
> +#define mask_store_direct { 3, 2, true }
> #define store_lanes_direct { 0, 0, false }
> #define mask_store_lanes_direct { 0, 0, false }
> #define scatter_store_direct { 3, 3, false }
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/mask_load_slp_1.c b/gcc/testsuite/gcc.target/aarch64/sve/mask_load_slp_1.c
> new file mode 100644
> index 0000000..b106cae
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/mask_load_slp_1.c
> @@ -0,0 +1,74 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -ftree-vectorize" } */
> +
> +#include <stdint.h>
> +
> +#define MASK_SLP_2(TYPE_COND, ALT_VAL) \
> +void __attribute__ ((noinline, noclone)) \
> +mask_slp_##TYPE_COND##_2_##ALT_VAL (int *restrict x, int *restrict y, \
> + TYPE_COND *restrict z, int n) \
> +{ \
> + for (int i = 0; i < n; i += 2) \
> + { \
> + x[i] = y[i] ? z[i] : 1; \
> + x[i + 1] = y[i + 1] ? z[i + 1] : ALT_VAL; \
> + } \
> +}
> +
> +#define MASK_SLP_4(TYPE_COND, ALT_VAL) \
> +void __attribute__ ((noinline, noclone)) \
> +mask_slp_##TYPE_COND##_4_##ALT_VAL (int *restrict x, int *restrict y, \
> + TYPE_COND *restrict z, int n) \
> +{ \
> + for (int i = 0; i < n; i += 4) \
> + { \
> + x[i] = y[i] ? z[i] : 1; \
> + x[i + 1] = y[i + 1] ? z[i + 1] : ALT_VAL; \
> + x[i + 2] = y[i + 2] ? z[i + 2] : 1; \
> + x[i + 3] = y[i + 3] ? z[i + 3] : ALT_VAL; \
> + } \
> +}
> +
> +#define MASK_SLP_8(TYPE_COND, ALT_VAL) \
> +void __attribute__ ((noinline, noclone)) \
> +mask_slp_##TYPE_COND##_8_##ALT_VAL (int *restrict x, int *restrict y, \
> + TYPE_COND *restrict z, int n) \
> +{ \
> + for (int i = 0; i < n; i += 8) \
> + { \
> + x[i] = y[i] ? z[i] : 1; \
> + x[i + 1] = y[i + 1] ? z[i + 1] : ALT_VAL; \
> + x[i + 2] = y[i + 2] ? z[i + 2] : 1; \
> + x[i + 3] = y[i + 3] ? z[i + 3] : ALT_VAL; \
> + x[i + 4] = y[i + 4] ? z[i + 4] : 1; \
> + x[i + 5] = y[i + 5] ? z[i + 5] : ALT_VAL; \
> + x[i + 6] = y[i + 6] ? z[i + 6] : 1; \
> + x[i + 7] = y[i + 7] ? z[i + 7] : ALT_VAL; \
> + } \
> +}
> +
> +MASK_SLP_2(int8_t, 1)
> +MASK_SLP_2(int8_t, 2)
> +MASK_SLP_2(int, 1)
> +MASK_SLP_2(int, 2)
> +MASK_SLP_2(int64_t, 1)
> +MASK_SLP_2(int64_t, 2)
> +
> +MASK_SLP_4(int8_t, 1)
> +MASK_SLP_4(int8_t, 2)
> +MASK_SLP_4(int, 1)
> +MASK_SLP_4(int, 2)
> +MASK_SLP_4(int64_t, 1)
> +MASK_SLP_4(int64_t, 2)
> +
> +MASK_SLP_8(int8_t, 1)
> +MASK_SLP_8(int8_t, 2)
> +MASK_SLP_8(int, 1)
> +MASK_SLP_8(int, 2)
> +MASK_SLP_8(int64_t, 1)
> +MASK_SLP_8(int64_t, 2)
> +
> +/* { dg-final { scan-assembler-not {\tld2w\t} } } */
> +/* { dg-final { scan-assembler-not {\tst2w\t} } } */
> +/* { dg-final { scan-assembler-times {\tld1w\t} 48 } } */
> +/* { dg-final { scan-assembler-times {\tst1w\t} 40 } } */
> diff --git a/gcc/tree-data-ref.c b/gcc/tree-data-ref.c
> index 7d1f03c..1833a5f 100644
> --- a/gcc/tree-data-ref.c
> +++ b/gcc/tree-data-ref.c
> @@ -1272,7 +1272,7 @@ create_data_ref (edge nest, loop_p loop, tree memref, gimple *stmt,
> return dr;
> }
>
> -/* A helper function computes order between two tree epxressions T1 and T2.
> +/* A helper function computes order between two tree expressions T1 and T2.
> This is used in comparator functions sorting objects based on the order
> of tree expressions. The function returns -1, 0, or 1. */
>
> diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c
> index 7bbd47f..8a82147 100644
> --- a/gcc/tree-vect-data-refs.c
> +++ b/gcc/tree-vect-data-refs.c
> @@ -2837,22 +2837,72 @@ can_group_stmts_p (stmt_vec_info stmt1_info, stmt_vec_info stmt2_info)
> if (ifn != gimple_call_internal_fn (call2))
> return false;
>
> - /* Check that the masks are the same. Cope with casts of masks,
> + /* Check that the masks can be combined. */
> + tree mask1 = gimple_call_arg (call1, 2);
> + tree mask2 = gimple_call_arg (call2, 2);
> + if (!operand_equal_p (mask1, mask2, 0))
> + {
> + /* Stores need identical masks. */
> + if (ifn == IFN_MASK_STORE)
> + {
> + mask1 = strip_conversion (mask1);
> + if (!mask1)
> + return false;
> + mask2 = strip_conversion (mask2);
> + if (!mask2)
> + return false;
> + if (!operand_equal_p (mask1, mask2, 0))
> + return false;
> + }
> + /* Loads are allowed different masks under SLP only.
> + (See slp_vect_only_p () below). */
> + }
> + return true;
> + }
> +
> + return false;
> +}
> +
> +/* Return true if vectorizable_* routines can handle statements STMT1_INFO
> + and STMT2_INFO being in a single group for SLP only. */
> +
> +static bool
> +slp_vect_only_p (stmt_vec_info stmt1_info, stmt_vec_info stmt2_info)
> +{
> + if (gimple_assign_single_p (stmt1_info->stmt))
> + {
> + gcc_assert (gimple_assign_single_p (stmt2_info->stmt));
> + return false;
> + }
> +
> + gcall *call1 = dyn_cast <gcall *> (stmt1_info->stmt);
> + if (call1 && gimple_call_internal_p (call1))
> + {
> + /* Check for two masked loads or two masked stores. */
> + gcall *call2 = dyn_cast <gcall *> (stmt2_info->stmt);
> + gcc_assert (call2 && gimple_call_internal_p (call2));
> + internal_fn ifn = gimple_call_internal_fn (call1);
> + if (ifn != IFN_MASK_LOAD)
> + return false;
> + gcc_assert (ifn == gimple_call_internal_fn (call2));
> +
> + /* Check if the masks are the same. Cope with casts of masks,
> like those created by build_mask_conversion. */
> tree mask1 = gimple_call_arg (call1, 2);
> tree mask2 = gimple_call_arg (call2, 2);
> if (!operand_equal_p (mask1, mask2, 0))
> {
> + /* This is the only case that is just for SLP: non-identical but
> + otherwise slp-compatible masks. */
> mask1 = strip_conversion (mask1);
> if (!mask1)
> - return false;
> + return true;
> mask2 = strip_conversion (mask2);
> if (!mask2)
> - return false;
> + return true;
> if (!operand_equal_p (mask1, mask2, 0))
> - return false;
> + return true;
> }
> - return true;
> }
>
> return false;
Normally I'd say it would be better to add a bool argument to
can_group_stmts_p that says whether we want non-SLP-only rules,
or perhaps convert the return type to an enum. But given that the
non-SLP path is going away soon anyway, I guess separate functions
are better despite the cut-&-paste.
> diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c
> index afbf9a9..754a2e4 100644
> --- a/gcc/tree-vect-loop.c
> +++ b/gcc/tree-vect-loop.c
> @@ -1755,6 +1755,49 @@ vect_get_datarefs_in_loop (loop_p loop, basic_block *bbs,
> return opt_result::success ();
> }
>
> +/* Look for SLP-only access groups and turn each individual access into its own
> + group. */
> +static void
> +vect_dissolve_slp_only_groups (loop_vec_info loop_vinfo)
> +{
> + unsigned int i;
> + struct data_reference *dr;
> +
> + DUMP_VECT_SCOPE ("vect_dissolve_slp_only_groups");
> +
> + vec<data_reference_p> datarefs = loop_vinfo->shared->datarefs;
> + FOR_EACH_VEC_ELT (datarefs, i, dr)
> + {
> + gcc_assert (DR_REF (dr));
> + stmt_vec_info stmt_info = loop_vinfo->lookup_stmt (DR_STMT (dr));
> +
> + /* Check if the load is a part of an interleaving chain. */
> + if (STMT_VINFO_GROUPED_ACCESS (stmt_info))
> + {
> + stmt_vec_info first_element = DR_GROUP_FIRST_ELEMENT (stmt_info);
> + unsigned int group_size = DR_GROUP_SIZE (first_element);
> +
> + /* Check if SLP-only groups. */
> + if (STMT_VINFO_SLP_VECT_ONLY (first_element))
> + {
> + /* Dissolve the group. */
> + STMT_VINFO_SLP_VECT_ONLY (first_element) = false;
> +
> + stmt_vec_info vinfo = first_element;
> + while (vinfo)
> + {
> + stmt_vec_info next = DR_GROUP_NEXT_ELEMENT (vinfo);
> + DR_GROUP_FIRST_ELEMENT (vinfo) = NULL;
> + DR_GROUP_NEXT_ELEMENT (vinfo) = NULL;
> + DR_GROUP_SIZE (vinfo) = 1;
> + DR_GROUP_GAP (vinfo) = group_size - 1;
> + vinfo = next;
I think DR_GROUP_FIRST_ELEMENT should be vinfo here, so that it remains
a grouped access with only one element.
> + }
Formatting nit: this block is indented two columns too far.
> diff --git a/gcc/tree-vect-slp.c b/gcc/tree-vect-slp.c
> index 0e15087d..ebc4432 100644
> --- a/gcc/tree-vect-slp.c
> +++ b/gcc/tree-vect-slp.c
> @@ -325,6 +325,14 @@ vect_get_and_check_slp_defs (vec_info *vinfo, unsigned char *swap,
> {
> internal_fn ifn = gimple_call_internal_fn (stmt);
> commutative_op = first_commutative_argument (ifn);
> +
> + /* Masked load, only look at mask. */
> + if (ifn == IFN_MASK_LOAD)
> + {
> + number_of_oprnds = 1;
> + /* Mask operand index. */
> + first_op_idx = 5;
> + }
> }
> }
> else if (gassign *stmt = dyn_cast <gassign *> (stmt_info->stmt))
> @@ -624,7 +632,7 @@ vect_two_operations_perm_ok_p (vec<stmt_vec_info> stmts,
> is false then this indicates the comparison could not be
> carried out or the stmts will never be vectorized by SLP.
>
> - Note COND_EXPR is possibly ismorphic to another one after swapping its
> + Note COND_EXPR is possibly isomorphic to another one after swapping its
> operands. Set SWAP[i] to 1 if stmt I is COND_EXPR and isomorphic to
> the first stmt by swapping the two operands of comparison; set SWAP[i]
> to 2 if stmt I is isormorphic to the first stmt by inverting the code
> @@ -1146,13 +1154,23 @@ vect_build_slp_tree_2 (vec_info *vinfo,
> &this_max_nunits, matches, &two_operators))
> return NULL;
>
> - /* If the SLP node is a load, terminate the recursion. */
> + /* If the SLP node is a load, terminate the recursion unless masked. */
> if (STMT_VINFO_GROUPED_ACCESS (stmt_info)
> && DR_IS_READ (STMT_VINFO_DATA_REF (stmt_info)))
> {
> - *max_nunits = this_max_nunits;
> - node = vect_create_new_slp_node (stmts);
> - return node;
> + if (gcall *stmt = dyn_cast <gcall *> (stmt_info->stmt))
> + {
> + /* Masked load. */
> + gcc_assert (gimple_call_internal_p (stmt));
> + gcc_assert (gimple_call_internal_fn (stmt) == IFN_MASK_LOAD);
Normal GCC style is to have a single assert with '&&'.
Looks good to me otherwise, but Richard B should have the final say.
Thanks,
Richard
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