Add QI vector mode support to by-pieces for memset

1. Replace scalar_int_mode with fixed_size_mode in the by-pieces
infrastructure to allow non-integer mode.
2. Rename widest_int_mode_for_size to widest_fixed_size_mode_for_size
to return QI vector mode for memset.
3. Add op_by_pieces_d::smallest_fixed_size_mode_for_size to return the
smallest integer or QI vector mode.
4. Remove clear_by_pieces_1 and use builtin_memset_read_str in
clear_by_pieces to support vector mode broadcast.
5. Add lowpart_subreg_regno, a wrapper around simplify_subreg_regno that
uses subreg_lowpart_offset (mode, prev_mode) as the offset.
6. Add TARGET_GEN_MEMSET_SCRATCH_RTX to allow the backend to use a hard
scratch register to avoid stack realignment when expanding memset.

gcc/

	PR middle-end/90773
	* builtins.c (builtin_memcpy_read_str): Change the mode argument
	from scalar_int_mode to fixed_size_mode.
	(builtin_strncpy_read_str): Likewise.
	(gen_memset_value_from_prev): New function.
	(builtin_memset_read_str): Change the mode argument from
	scalar_int_mode to fixed_size_mode.  Use gen_memset_value_from_prev
	and support CONST_VECTOR.
	(builtin_memset_gen_str): Likewise.
	(try_store_by_multiple_pieces): Use by_pieces_constfn to declare
	constfun.
	* builtins.h (builtin_strncpy_read_str): Replace scalar_int_mode
	with fixed_size_mode.
	(builtin_memset_read_str): Likewise.
	* expr.c (widest_int_mode_for_size): Renamed to ...
	(widest_fixed_size_mode_for_size): Add a bool argument to
	indicate if QI vector mode can be used.
	(by_pieces_ninsns): Call widest_fixed_size_mode_for_size
	instead of widest_int_mode_for_size.
	(pieces_addr::adjust): Change the mode argument from
	scalar_int_mode to fixed_size_mode.
	(op_by_pieces_d): Make m_len read-only.  Add a bool member,
	m_qi_vector_mode, to indicate that QI vector mode can be used.
	(op_by_pieces_d::op_by_pieces_d): Add a bool argument to
	initialize m_qi_vector_mode.  Call widest_fixed_size_mode_for_size
	instead of widest_int_mode_for_size.
	(op_by_pieces_d::get_usable_mode): Change the mode argument from
	scalar_int_mode to fixed_size_mode.  Call
	widest_fixed_size_mode_for_size instead of
	widest_int_mode_for_size.
	(op_by_pieces_d::smallest_fixed_size_mode_for_size): New member
	function to return the smallest integer or QI vector mode.
	(op_by_pieces_d::run): Call widest_fixed_size_mode_for_size
	instead of widest_int_mode_for_size.  Call
	smallest_fixed_size_mode_for_size instead of
	smallest_int_mode_for_size.
	(store_by_pieces_d::store_by_pieces_d): Add a bool argument to
	indicate that QI vector mode can be used and pass it to
	op_by_pieces_d::op_by_pieces_d.
	(can_store_by_pieces): Call widest_fixed_size_mode_for_size
	instead of widest_int_mode_for_size.  Pass memsetp to
	widest_fixed_size_mode_for_size to support QI vector mode.
	Allow all CONST_VECTORs for memset if vec_duplicate is supported.
	(store_by_pieces): Pass memsetp to
	store_by_pieces_d::store_by_pieces_d.
	(clear_by_pieces_1): Removed.
	(clear_by_pieces): Replace clear_by_pieces_1 with
	builtin_memset_read_str and pass true to store_by_pieces_d to
	support vector mode broadcast.
	(string_cst_read_str): Change the mode argument from
	scalar_int_mode to fixed_size_mode.
	* expr.h (by_pieces_constfn): Change scalar_int_mode to
	fixed_size_mode.
	(by_pieces_prev): Likewise.
	* rtl.h (lowpart_subreg_regno): New.
	* rtlanal.c (lowpart_subreg_regno): New.  A wrapper around
	simplify_subreg_regno.
	* target.def (gen_memset_scratch_rtx): New hook.
	* doc/tm.texi.in: Add TARGET_GEN_MEMSET_SCRATCH_RTX.
	* doc/tm.texi: Regenerated.

gcc/testsuite/

	* gcc.target/i386/pr100865-3.c: Expect vmovdqu8 instead of
	vmovdqu.
	* gcc.target/i386/pr100865-4b.c: Likewise.

1 files changed, 2 insertions, 0 deletions

diff --git a/gcc/rtl.h b/gcc/rtl.h
index 5ffe900..5fdcdfc 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -2460,6 +2460,8 @@ extern bool subreg_offset_representable_p (unsigned int, machine_mode,
 extern unsigned int subreg_regno (const_rtx);
 extern int simplify_subreg_regno (unsigned int, machine_mode,
 				  poly_uint64, machine_mode);
+extern int lowpart_subreg_regno (unsigned int, machine_mode,
+				 machine_mode);
 extern unsigned int subreg_nregs (const_rtx);
 extern unsigned int subreg_nregs_with_regno (unsigned int, const_rtx);
 extern unsigned HOST_WIDE_INT nonzero_bits (const_rtx, machine_mode);