middle-end: Allow _BitInt(65535) [PR102989]

middle-end: Allow _BitInt(65535) [PR102989]

The following patch lifts further restrictions which limited _BitInt to at
most 16319 bits up to 65535.
The problem was mainly in INTEGER_CST representation, which had 3
unsigned char members to describe lengths in number of 64-bit limbs, which
it wanted to fit into 32 bits.  This patch removes the third one which was
just a cache to save a few compile time cycles for wi::to_offset and
enlarges the other two members to unsigned short.
Furthermore, the same problem has been in some uses of trailing_wide_int*
(in value-range-storage*) and value-range-storage* itself, while other
uses of trailing_wide_int* have been fine (e.g. CONST_POLY_INT, where no
constants will be larger than 3/5/9/11 limbs depending on target, so 255
limit is plenty).  The patch turns all those length representations to be
unsigned short for consistency, so value-range-storage* can handle even
16320-65535 bits BITINT_TYPE ranges.  The cc1plus growth is about 16K,
so not really significant for 38M .text section.

Note, the reason for the new limit is
  unsigned int precision : 16;
TYPE_PRECISION limit, if we wanted to overcome that, TYPE_PRECISION would
need to use some other member for BITINT_TYPE from all the others and
we could reach that way 4194239 limit (65535 * 64 - 1, again implied by
INTEGER_CST and value-range-storage*).  Dunno if that is
worth it or if it is something we want to do for GCC 14 though.

2023-10-14  Jakub Jelinek  <jakub@redhat.com>

	PR c/102989
gcc/
	* tree-core.h (struct tree_base): Remove int_length.offset
	member, change type of int_length.unextended and int_length.extended
	from unsigned char to unsigned short.
	* tree.h (TREE_INT_CST_OFFSET_NUNITS): Remove.
	(wi::extended_tree <N>::get_len): Don't use TREE_INT_CST_OFFSET_NUNITS,
	instead compute it at runtime from TREE_INT_CST_EXT_NUNITS and
	TREE_INT_CST_NUNITS.
	* tree.cc (wide_int_to_tree_1): Don't assert
	TREE_INT_CST_OFFSET_NUNITS value.
	(make_int_cst): Don't initialize TREE_INT_CST_OFFSET_NUNITS.
	* wide-int.h (WIDE_INT_MAX_ELTS): Change from 255 to 1024.
	(WIDEST_INT_MAX_ELTS): Change from 510 to 2048, adjust comment.
	(trailing_wide_int_storage): Change m_len type from unsigned char *
	to unsigned short *.
	(trailing_wide_int_storage::trailing_wide_int_storage): Change second
	argument from unsigned char * to unsigned short *.
	(trailing_wide_ints): Change m_max_len type from unsigned char to
	unsigned short.  Change m_len element type from
	struct{unsigned char len;} to unsigned short.
	(trailing_wide_ints <N>::operator []): Remove .len from m_len
	accesses.
	* value-range-storage.h (irange_storage::lengths_address): Change
	return type from const unsigned char * to const unsigned short *.
	(irange_storage::write_lengths_address): Change return type from
	unsigned char * to unsigned short *.
	* value-range-storage.cc (irange_storage::write_lengths_address):
	Likewise.
	(irange_storage::lengths_address): Change return type from
	const unsigned char * to const unsigned short *.
	(write_wide_int): Change len argument type from unsigned char *&
	to unsigned short *&.
	(irange_storage::set_irange): Change len variable type from
	unsigned char * to unsigned short *.
	(read_wide_int): Change len argument type from unsigned char to
	unsigned short.  Use trailing_wide_int_storage <unsigned short>
	instead of trailing_wide_int_storage and
	trailing_wide_int <unsigned short> instead of trailing_wide_int.
	(irange_storage::get_irange): Change len variable type from
	unsigned char * to unsigned short *.
	(irange_storage::size): Multiply n by sizeof (unsigned short)
	in len_size variable initialization.
	(irange_storage::dump): Change len variable type from
	unsigned char * to unsigned short *.
gcc/cp/
	* module.cc (trees_out::start, trees_in::start): Remove
	TREE_INT_CST_OFFSET_NUNITS handling.
gcc/testsuite/
	* gcc.dg/bitint-38.c: Change into dg-do run test, in addition
	to checking the addition, division and right shift results at compile
	time check it also at runtime.
	* gcc.dg/bitint-39.c: New test.