On Fri, 11 Aug 2023, juzhe.zh...@rivai.ai wrote:
> From: Ju-Zhe Zhong <juzhe.zh...@rivai.ai>
>
> Hi, Richard and Richi.
>
> This patch add support live vectorization by VEC_EXTRACT for LEN loop control.
>
> Consider this following case:
>
> #include <stdint.h>
>
> #define EXTRACT_LAST(TYPE) \
> TYPE __attribute__ ((noinline, noclone)) \
> test_##TYPE (TYPE *x, int n, TYPE value) \
> { \
> TYPE last; \
> for (int j = 0; j < n; ++j) \
> { \
> last = x[j]; \
> x[j] = last * value; \
> } \
> return last; \
> }
>
> #define TEST_ALL(T) \
> T (uint8_t) \
>
> TEST_ALL (EXTRACT_LAST)
>
> ARM SVE IR:
>
> Preheader:
> max_mask_34 = .WHILE_ULT (0, bnd.5_6, { 0, ... });
>
> Loop:
> ...
> # loop_mask_22 = PHI <next_mask_35(4), max_mask_34(3)>
> ...
> vect_last_12.8_23 = .MASK_LOAD (_7, 8B, loop_mask_22);
> vect__4.9_27 = vect_last_12.8_23 * vect_cst__26;
> .MASK_STORE (_7, 8B, loop_mask_22, vect__4.9_27);
> ...
> next_mask_35 = .WHILE_ULT (_1, bnd.5_6, { 0, ... });
> ...
>
> Epilogue:
> _25 = .EXTRACT_LAST (loop_mask_22, vect_last_12.8_23);
>
> For RVV since we prefer len in loop control, after this patch for RVV:
>
> Loop:
> ...
> loop_len_22 = SELECT_VL;
> vect_last_12.8_23 = .MASK_LOAD (_7, 8B, loop_len_22);
> vect__4.9_27 = vect_last_12.8_23 * vect_cst__26;
> .MASK_STORE (_7, 8B, loop_len_22, vect__4.9_27);
> ...
>
> Epilogue:
> _25 = .VEC_EXTRACT (loop_len_22 + bias - 1, vect_last_12.8_23);
>
> Details of this approach:
>
> 1. Step 1 - Add 'vect_can_vectorize_extract_last_with_len_p' to enable live
> vectorization
> for LEN loop control.
>
> This function we check whether target support:
> - Use LEN as the loop control.
> - Support VEC_EXTRACT optab.
>
> 2. Step 2 - Record LEN for loop control if
> 'vect_can_vectorize_extract_last_with_len_p' is true.
>
> 3. Step 3 - Gerenate VEC_EXTRACT (v, LEN + BIAS - 1).
>
> The only difference between mask and len is that len is using length
> generated by SELECT_VL and
> use VEC_EXTRACT pattern. The rest of the live vectorization is totally the
> same ARM SVE.
>
> Bootstrap and Regression on X86 passed.
>
> Tested on ARM QEMU.
>
> Ok for trunk?
>
> gcc/ChangeLog:
>
> * tree-vect-loop.cc (vect_can_vectorize_extract_last_with_len_p): New
> function.
> (vectorizable_live_operation): Add loop len control.
>
> ---
> gcc/tree-vect-loop.cc | 76 +++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 70 insertions(+), 6 deletions(-)
>
> diff --git a/gcc/tree-vect-loop.cc b/gcc/tree-vect-loop.cc
> index bf8d677b584..809b73b966c 100644
> --- a/gcc/tree-vect-loop.cc
> +++ b/gcc/tree-vect-loop.cc
> @@ -8963,6 +8963,27 @@ vect_can_vectorize_without_simd_p (code_helper code)
> && vect_can_vectorize_without_simd_p (tree_code (code)));
> }
>
> +/* Return true if target supports extract last vectorization with LEN. */
> +
> +static bool
> +vect_can_vectorize_extract_last_with_len_p (tree vectype)
> +{
> + /* Return false if target doesn't support LEN in loop control. */
> + machine_mode vmode;
> + machine_mode vec_mode = TYPE_MODE (vectype);
> + if (!VECTOR_MODE_P (vec_mode))
> + return false;
> + if (!get_len_load_store_mode (vec_mode, true).exists (&vmode)
> + || !get_len_load_store_mode (vec_mode, false).exists (&vmode))
> + return false;
So this "hidden" bit in the end decides whether to ...
> + /* Target need to support VEC_EXTRACT to extract the last active element.
> */
> + return convert_optab_handler (vec_extract_optab,
> + vec_mode,
> + TYPE_MODE (TREE_TYPE (vectype)))
> + != CODE_FOR_nothing;
> +}
> +
> /* Create vector init for vectorized iv. */
> static tree
> vect_create_nonlinear_iv_init (gimple_seq* stmts, tree init_expr,
> @@ -10279,7 +10300,8 @@ vectorizable_live_operation (vec_info *vinfo,
> stmt_vec_info stmt_info,
> if (loop_vinfo && LOOP_VINFO_CAN_USE_PARTIAL_VECTORS_P (loop_vinfo))
> {
> if (!direct_internal_fn_supported_p (IFN_EXTRACT_LAST, vectype,
> - OPTIMIZE_FOR_SPEED))
> + OPTIMIZE_FOR_SPEED)
> + && !vect_can_vectorize_extract_last_with_len_p (vectype))
> {
> if (dump_enabled_p ())
> dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> @@ -10308,9 +10330,14 @@ vectorizable_live_operation (vec_info *vinfo,
> stmt_vec_info stmt_info,
> else
> {
> gcc_assert (ncopies == 1 && !slp_node);
> - vect_record_loop_mask (loop_vinfo,
> - &LOOP_VINFO_MASKS (loop_vinfo),
> - 1, vectype, NULL);
> + if (vect_can_vectorize_extract_last_with_len_p (vectype))
> + vect_record_loop_len (loop_vinfo,
> + &LOOP_VINFO_LENS (loop_vinfo),
> + 1, vectype, 1);
.. record a loop_len here. I think powerpc at least has .VEC_EXTRACT as
well but of course .VEC_EXTRACT support itself doesn't have anything to
do with 'len' support.
x86 has .VEC_SET but not yet .VEC_EXTRACT, if it gets .VEC_EXTRACT
its partial vector support still wants masks, not lens (and once
we record both we fail).
So how can we resolve the issue when a non-VL operation like
.VEC_EXTRACT is used for _len support?
Note x86 doens't yet support IFN_EXTRACT_LAST either.
So, why do we test for get_len_load_store_mode and not just for
VEC_EXTRACT?
> + else
> + vect_record_loop_mask (loop_vinfo,
> + &LOOP_VINFO_MASKS (loop_vinfo),
> + 1, vectype, NULL);
> }
> }
> /* ??? Enable for loop costing as well. */
> @@ -10336,7 +10363,9 @@ vectorizable_live_operation (vec_info *vinfo,
> stmt_vec_info stmt_info,
> gimple *vec_stmt;
> if (slp_node)
> {
> - gcc_assert (!loop_vinfo || !LOOP_VINFO_FULLY_MASKED_P (loop_vinfo));
> + gcc_assert (!loop_vinfo
> + || (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo)
> + && !LOOP_VINFO_FULLY_WITH_LENGTH_P (loop_vinfo)));
>
> /* Get the correct slp vectorized stmt. */
> vec_lhs = SLP_TREE_VEC_DEFS (slp_node)[vec_entry];
> @@ -10380,7 +10409,42 @@ vectorizable_live_operation (vec_info *vinfo,
> stmt_vec_info stmt_info,
>
> gimple_seq stmts = NULL;
> tree new_tree;
> - if (LOOP_VINFO_FULLY_MASKED_P (loop_vinfo))
> + if (LOOP_VINFO_FULLY_WITH_LENGTH_P (loop_vinfo))
> + {
> + /* Emit:
> +
> + SCALAR_RES = VEC_EXTRACT <VEC_LHS, LEN + BIAS - 1>
> +
> + where VEC_LHS is the vectorized live-out result and MASK is
> + the loop mask for the final iteration. */
> + gcc_assert (ncopies == 1 && !slp_node);
> + gimple_seq tem = NULL;
> + gimple_stmt_iterator gsi = gsi_last (tem);
> + tree len
> + = vect_get_loop_len (loop_vinfo, &gsi,
> + &LOOP_VINFO_LENS (loop_vinfo),
> + 1, vectype, 0, 0);
> +
> + /* BIAS - 1. */
> + signed char biasval = LOOP_VINFO_PARTIAL_LOAD_STORE_BIAS (loop_vinfo);
> + tree bias_minus_one
> + = int_const_binop (MINUS_EXPR,
> + build_int_cst (TREE_TYPE (len), biasval),
> + build_one_cst (TREE_TYPE (len)));
> +
> + /* LAST_INDEX = LEN + (BIAS - 1). */
> + tree last_index = gimple_build (&stmts, PLUS_EXPR, TREE_TYPE (len),
> + len, bias_minus_one);
> +
> + /* SCALAR_RES = VEC_EXTRACT <VEC_LHS, LEN + BIAS - 1>. */
> + tree scalar_res
> + = gimple_build (&stmts, CFN_VEC_EXTRACT, TREE_TYPE (vectype),
> + vec_lhs_phi, last_index);
> +
can we double-check this on powerpc and s390?
Thanks,
Richard.
> + /* Convert the extracted vector element to the scalar type. */
> + new_tree = gimple_convert (&stmts, lhs_type, scalar_res);
> + }
> + else if (LOOP_VINFO_FULLY_MASKED_P (loop_vinfo))
> {
> /* Emit:
>
