"H.J. Lu via Gcc-patches" <gcc-patches@gcc.gnu.org> writes:
> 1. Rewrite builtin_memset_read_str and builtin_memset_gen_str with
> vec_duplicate_optab to duplicate QI value to TI/OI/XI value.
> 2. Add TARGET_GEN_MEMSET_SCRATCH_RTX to allow the backend to use a hard
> scratch register to avoid stack realignment when expanding memset.
>
> PR middle-end/90773
> * builtins.c (gen_memset_value_from_prev): New function.
> (gen_memset_broadcast): Likewise.
> (builtin_memset_read_str): Use gen_memset_value_from_prev
> and gen_memset_broadcast.
> (builtin_memset_gen_str): Likewise.
> * target.def (gen_memset_scratch_rtx): New hook.
> * doc/tm.texi.in: Add TARGET_GEN_MEMSET_SCRATCH_RTX.
> * doc/tm.texi: Regenerated.
> ---
> gcc/builtins.c | 123 +++++++++++++++++++++++++++++++++++++--------
> gcc/doc/tm.texi | 5 ++
> gcc/doc/tm.texi.in | 2 +
> gcc/target.def | 7 +++
> 4 files changed, 116 insertions(+), 21 deletions(-)
>
> diff --git a/gcc/builtins.c b/gcc/builtins.c
> index 39ab139b7e1..c1758ae2efc 100644
> --- a/gcc/builtins.c
> +++ b/gcc/builtins.c
> @@ -6686,26 +6686,111 @@ expand_builtin_strncpy (tree exp, rtx target)
> return NULL_RTX;
> }
>
> -/* Callback routine for store_by_pieces. Read GET_MODE_BITSIZE (MODE)
> - bytes from constant string DATA + OFFSET and return it as target
> - constant. If PREV isn't nullptr, it has the RTL info from the
> +/* Return the RTL of a register in MODE generated from PREV in the
> previous iteration. */
>
> -rtx
> -builtin_memset_read_str (void *data, void *prevp,
> - HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> - scalar_int_mode mode)
> +static rtx
> +gen_memset_value_from_prev (void *prevp, scalar_int_mode mode)
> {
> + rtx target = nullptr;
> by_pieces_prev *prev = (by_pieces_prev *) prevp;
> if (prev != nullptr && prev->data != nullptr)
> {
> /* Use the previous data in the same mode. */
> if (prev->mode == mode)
> return prev->data;
> +
> + rtx prev_rtx = prev->data;
> + machine_mode prev_mode = prev->mode;
> + unsigned int word_size = GET_MODE_SIZE (word_mode);
> + if (word_size < GET_MODE_SIZE (prev->mode)
> + && word_size > GET_MODE_SIZE (mode))
> + {
> + /* First generate subreg of word mode if the previous mode is
> + wider than word mode and word mode is wider than MODE. */
> + prev_rtx = simplify_gen_subreg (word_mode, prev_rtx,
> + prev_mode, 0);
> + prev_mode = word_mode;
> + }
> + if (prev_rtx != nullptr)
> + target = simplify_gen_subreg (mode, prev_rtx, prev_mode, 0);
> }
> + return target;
> +}
> +
> +/* Return the RTL of a register in MODE broadcasted from DATA. */
> +
> +static rtx
> +gen_memset_broadcast (rtx data, scalar_int_mode mode)
> +{
> + /* Skip if regno_reg_rtx isn't initialized. */
> + if (!regno_reg_rtx)
> + return nullptr;
> +
> + rtx target = nullptr;
> +
> + unsigned int nunits = GET_MODE_SIZE (mode) / GET_MODE_SIZE (QImode);
> + machine_mode vector_mode;
> + if (!mode_for_vector (QImode, nunits).exists (&vector_mode))
> + gcc_unreachable ();
Sorry, I realise it's a bit late to be raising this objection now,
but I don't think it's a good idea to use scalar integer modes as
a proxy for vector modes. In principle there's no reason why a
target has to define an integer mode for every vector mode.
If we want the mode to be a vector then I think the by-pieces
infrastructure should be extended to support vectors directly,
rather than assuming that each piece can be represented as
a scalar_int_mode.
Thanks,
Richard
> +
> + enum insn_code icode = optab_handler (vec_duplicate_optab,
> + vector_mode);
> + if (icode != CODE_FOR_nothing)
> + {
> + rtx reg = targetm.gen_memset_scratch_rtx (vector_mode);
> + if (CONST_INT_P (data))
> + {
> + /* Use the move expander with CONST_VECTOR. */
> + rtx const_vec = gen_const_vec_duplicate (vector_mode, data);
> + emit_move_insn (reg, const_vec);
> + }
> + else
> + {
> +
> + class expand_operand ops[2];
> + create_output_operand (&ops[0], reg, vector_mode);
> + create_input_operand (&ops[1], data, QImode);
> + expand_insn (icode, 2, ops);
> + if (!rtx_equal_p (reg, ops[0].value))
> + emit_move_insn (reg, ops[0].value);
> + }
> + target = lowpart_subreg (mode, reg, vector_mode);
> + }
> +
> + return target;
> +}
> +
> +/* Callback routine for store_by_pieces. Read GET_MODE_BITSIZE (MODE)
> + bytes from constant string DATA + OFFSET and return it as target
> + constant. If PREV isn't nullptr, it has the RTL info from the
> + previous iteration. */
>
> +rtx
> +builtin_memset_read_str (void *data, void *prev,
> + HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> + scalar_int_mode mode)
> +{
> + rtx target;
> const char *c = (const char *) data;
> - char *p = XALLOCAVEC (char, GET_MODE_SIZE (mode));
> + char *p;
> +
> + /* Don't use the previous value if size is 1. */
> + if (GET_MODE_SIZE (mode) != 1)
> + {
> + target = gen_memset_value_from_prev (prev, mode);
> + if (target != nullptr)
> + return target;
> +
> + p = XALLOCAVEC (char, GET_MODE_SIZE (QImode));
> + memset (p, *c, GET_MODE_SIZE (QImode));
> + rtx src = c_readstr (p, QImode);
> + target = gen_memset_broadcast (src, mode);
> + if (target != nullptr)
> + return target;
> + }
> +
> + p = XALLOCAVEC (char, GET_MODE_SIZE (mode));
>
> memset (p, *c, GET_MODE_SIZE (mode));
>
> @@ -6719,7 +6804,7 @@ builtin_memset_read_str (void *data, void *prevp,
> nullptr, it has the RTL info from the previous iteration. */
>
> static rtx
> -builtin_memset_gen_str (void *data, void *prevp,
> +builtin_memset_gen_str (void *data, void *prev,
> HOST_WIDE_INT offset ATTRIBUTE_UNUSED,
> scalar_int_mode mode)
> {
> @@ -6727,22 +6812,18 @@ builtin_memset_gen_str (void *data, void *prevp,
> size_t size;
> char *p;
>
> - by_pieces_prev *prev = (by_pieces_prev *) prevp;
> - if (prev != nullptr && prev->data != nullptr)
> - {
> - /* Use the previous data in the same mode. */
> - if (prev->mode == mode)
> - return prev->data;
> -
> - target = simplify_gen_subreg (mode, prev->data, prev->mode, 0);
> - if (target != nullptr)
> - return target;
> - }
> -
> size = GET_MODE_SIZE (mode);
> if (size == 1)
> return (rtx) data;
>
> + target = gen_memset_value_from_prev (prev, mode);
> + if (target != nullptr)
> + return target;
> +
> + target = gen_memset_broadcast ((rtx) data, mode);
> + if (target != nullptr)
> + return target;
> +
> p = XALLOCAVEC (char, size);
> memset (p, 1, size);
> coeff = c_readstr (p, mode);
> diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
> index 2a41ae5fba1..8849711fcf8 100644
> --- a/gcc/doc/tm.texi
> +++ b/gcc/doc/tm.texi
> @@ -12122,6 +12122,11 @@ This function prepares to emit a conditional
> comparison within a sequence
> @var{bit_code} is @code{AND} or @code{IOR}, which is the op on the compares.
> @end deftypefn
>
> +@deftypefn {Target Hook} rtx TARGET_GEN_MEMSET_SCRATCH_RTX (machine_mode
> @var{mode})
> +This hook should return an rtx for scratch register in @var{mode} to
> +be used by memset broadcast. The default is @code{gen_reg_rtx}.
> +@end deftypefn
> +
> @deftypefn {Target Hook} unsigned TARGET_LOOP_UNROLL_ADJUST (unsigned
> @var{nunroll}, class loop *@var{loop})
> This target hook returns a new value for the number of times @var{loop}
> should be unrolled. The parameter @var{nunroll} is the number of times
> diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
> index f881cdabe9e..a6bbf4f2667 100644
> --- a/gcc/doc/tm.texi.in
> +++ b/gcc/doc/tm.texi.in
> @@ -7958,6 +7958,8 @@ lists.
>
> @hook TARGET_GEN_CCMP_NEXT
>
> +@hook TARGET_GEN_MEMSET_SCRATCH_RTX
> +
> @hook TARGET_LOOP_UNROLL_ADJUST
>
> @defmac POWI_MAX_MULTS
> diff --git a/gcc/target.def b/gcc/target.def
> index c009671c583..5fb287db3bd 100644
> --- a/gcc/target.def
> +++ b/gcc/target.def
> @@ -2726,6 +2726,13 @@ DEFHOOK
> rtx, (rtx_insn **prep_seq, rtx_insn **gen_seq, rtx prev, int cmp_code, tree
> op0, tree op1, int bit_code),
> NULL)
>
> +DEFHOOK
> +(gen_memset_scratch_rtx,
> + "This hook should return an rtx for scratch register in @var{mode} to\n\
> +be used by memset broadcast. The default is @code{gen_reg_rtx}.",
> + rtx, (machine_mode mode),
> + gen_reg_rtx)
> +
> /* Return a new value for loop unroll size. */
> DEFHOOK
> (loop_unroll_adjust,
