Thanks for looking at this.
Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> writes:
> Hi,
> As mentioned in PR, for the following test-case:
>
> typedef unsigned char uint8_t;
>
> static inline uint8_t
> x264_clip_uint8(uint8_t x)
> {
> uint8_t t = -x;
> uint8_t t1 = x & ~63;
> return (t1 != 0) ? t : x;
> }
>
> void
> mc_weight(uint8_t *restrict dst, uint8_t *restrict src, int n)
> {
> for (int x = 0; x < n*16; x++)
> dst[x] = x264_clip_uint8(src[x]);
> }
>
> -O3 -mcpu=generic+sve generates following code for the inner loop:
>
> .L3:
> ld1b z0.b, p0/z, [x1, x2]
> movprfx z2, z0
> and z2.b, z2.b, #0xc0
> movprfx z1, z0
> neg z1.b, p1/m, z0.b
> cmpeq p2.b, p1/z, z2.b, #0
> sel z0.b, p2, z0.b, z1.b
> st1b z0.b, p0, [x0, x2]
> add x2, x2, x4
> whilelo p0.b, w2, w3
> b.any .L3
>
> The sel is redundant since we could conditionally negate z0 based on
> the predicate
> comparing z2 with 0.
>
> As suggested in the PR, the attached patch, introduces a new
> conditional internal function .COND_NEG, and in gimple-isel replaces
> the following sequence:
> op2 = -op1
> op0 = A cmp B
> lhs = op0 ? op1 : op2
>
> with:
> op0 = A inverted_cmp B
> lhs = .COND_NEG (op0, op1, op1).
>
> lhs = .COD_NEG (op0, op1, op1)
> implies
> lhs = neg (op1) if cond is true OR fall back to op1 if cond is false.
>
> With patch, it generates the following code-gen:
> .L3:
> ld1b z0.b, p0/z, [x1, x2]
> movprfx z1, z0
> and z1.b, z1.b, #0xc0
> cmpne p1.b, p2/z, z1.b, #0
> neg z0.b, p1/m, z0.b
> st1b z0.b, p0, [x0, x2]
> add x2, x2, x4
> whilelo p0.b, w2, w3
> b.any .L3
>
> While it seems to work for this test-case, I am not entirely sure if
> the patch is correct. Does it look in the right direction ?
For binary ops we use match.pd rather than isel:
(for uncond_op (UNCOND_BINARY)
cond_op (COND_BINARY)
(simplify
(vec_cond @0 (view_convert? (uncond_op@4 @1 @2)) @3)
(with { tree op_type = TREE_TYPE (@4); }
(if (vectorized_internal_fn_supported_p (as_internal_fn (cond_op), op_type)
&& is_truth_type_for (op_type, TREE_TYPE (@0)))
(view_convert (cond_op @0 @1 @2 (view_convert:op_type @3))))))
(simplify
(vec_cond @0 @1 (view_convert? (uncond_op@4 @2 @3)))
(with { tree op_type = TREE_TYPE (@4); }
(if (vectorized_internal_fn_supported_p (as_internal_fn (cond_op), op_type)
&& is_truth_type_for (op_type, TREE_TYPE (@0)))
(view_convert (cond_op (bit_not @0) @2 @3 (view_convert:op_type @1)))))))
I think it'd be good to do the same here, using new (UN)COND_UNARY
iterators. (The iterators will only have one value to start with,
but other unary ops could get the same treatment in future.)
Richard
>
> Thanks,
> Prathamesh
>
> diff --git a/gcc/gimple-isel.cc b/gcc/gimple-isel.cc
> index 38e90933c3e..5b0dd3c1993 100644
> --- a/gcc/gimple-isel.cc
> +++ b/gcc/gimple-isel.cc
> @@ -39,6 +39,8 @@ along with GCC; see the file COPYING3. If not see
> #include "optabs.h"
> #include "gimple-fold.h"
> #include "internal-fn.h"
> +#include "fold-const.h"
> +#include "tree-pretty-print.h"
>
> /* Expand all ARRAY_REF(VIEW_CONVERT_EXPR) gimple assignments into calls to
> internal function based on vector type of selected expansion.
> @@ -203,6 +205,35 @@ gimple_expand_vec_cond_expr (gimple_stmt_iterator *gsi,
> return new_stmt;
> }
>
> + /* Replace:
> + op2 = -op1
> + op0 = A cmp B
> + lhs = op0 ? op1 : op2
> +
> + with:
> + op0 = A inverted_cmp B
> + lhs = .COND_NEG (op0, op1, op1). */
> +
> + gassign *op1_def = nullptr;
> + if (TREE_CODE (op1) == SSA_NAME)
> + op1_def = static_cast<gassign *> (SSA_NAME_DEF_STMT (op1));
> +
> + gassign *op2_def = nullptr;
> + if (TREE_CODE (op2) == SSA_NAME)
> + op2_def = static_cast<gassign *> (SSA_NAME_DEF_STMT (op2));
> +
> + if (can_compute_op0 && op1_def && op2_def
> + && gimple_assign_rhs_code (op2_def) == NEGATE_EXPR
> + && operand_equal_p (gimple_assign_rhs1 (op2_def), op1, 0))
> + {
> + auto inverted_code
> + = invert_tree_comparison (gimple_assign_rhs_code (def_stmt),
> true);
> + gimple_assign_set_rhs_code (def_stmt, inverted_code);
> + auto gsi2 = gsi_for_stmt (op2_def);
> + gsi_remove (&gsi2, true);
> + return gimple_build_call_internal (IFN_COND_NEG, 3, op0, op1,
> op1);
> + }
> +
> if (can_compute_op0
> && used_vec_cond_exprs >= 2
> && (get_vcond_mask_icode (mode, TYPE_MODE (op0_type))
> diff --git a/gcc/internal-fn.c b/gcc/internal-fn.c
> index 78db25bbac4..b57c7a4ed3e 100644
> --- a/gcc/internal-fn.c
> +++ b/gcc/internal-fn.c
> @@ -3877,7 +3877,8 @@ static void (*const internal_fn_expanders[])
> (internal_fn, gcall *) = {
> T (BIT_IOR_EXPR, IFN_COND_IOR) \
> T (BIT_XOR_EXPR, IFN_COND_XOR) \
> T (LSHIFT_EXPR, IFN_COND_SHL) \
> - T (RSHIFT_EXPR, IFN_COND_SHR)
> + T (RSHIFT_EXPR, IFN_COND_SHR) \
> + T (NEGATE_EXPR, IFN_COND_NEG)
>
> /* Return a function that only performs CODE when a certain condition is met
> and that uses a given fallback value otherwise. For example, if CODE is
> diff --git a/gcc/internal-fn.def b/gcc/internal-fn.def
> index 88169ef4656..db40d1bfd18 100644
> --- a/gcc/internal-fn.def
> +++ b/gcc/internal-fn.def
> @@ -204,6 +204,8 @@ DEF_INTERNAL_OPTAB_FN (COND_FMS, ECF_CONST, cond_fms,
> cond_ternary)
> DEF_INTERNAL_OPTAB_FN (COND_FNMA, ECF_CONST, cond_fnma, cond_ternary)
> DEF_INTERNAL_OPTAB_FN (COND_FNMS, ECF_CONST, cond_fnms, cond_ternary)
>
> +DEF_INTERNAL_OPTAB_FN (COND_NEG, ECF_CONST | ECF_NOTHROW, cond_neg,
> cond_unary)
> +
> DEF_INTERNAL_OPTAB_FN (RSQRT, ECF_CONST, rsqrt, unary)
>
> DEF_INTERNAL_OPTAB_FN (REDUC_PLUS, ECF_CONST | ECF_NOTHROW,
> diff --git a/gcc/optabs.def b/gcc/optabs.def
> index 201b8aae1c0..fc65a3a7c23 100644
> --- a/gcc/optabs.def
> +++ b/gcc/optabs.def
> @@ -245,6 +245,7 @@ OPTAB_D (cond_fma_optab, "cond_fma$a")
> OPTAB_D (cond_fms_optab, "cond_fms$a")
> OPTAB_D (cond_fnma_optab, "cond_fnma$a")
> OPTAB_D (cond_fnms_optab, "cond_fnms$a")
> +OPTAB_D (cond_neg_optab, "cond_neg$a")
> OPTAB_D (cmov_optab, "cmov$a6")
> OPTAB_D (cstore_optab, "cstore$a4")
> OPTAB_D (ctrap_optab, "ctrap$a4")
