middle-end/104644 - recursion with bswap match.pd pattern

middle-end/104644 - recursion with bswap match.pd pattern

The following patch avoids infinite recursion during generic folding.
The (cmp (bswap @0) INTEGER_CST@1) simplification relies on
(bswap @1) actually being simplified, if it is not simplified, we just
move the bswap from one operand to the other and if @0 is also INTEGER_CST,
we apply the same rule next.

The reason why bswap @1 isn't folded to INTEGER_CST is that the INTEGER_CST
has TREE_OVERFLOW set on it and fold-const-call.cc predicate punts in
such cases:
static inline bool
integer_cst_p (tree t)
{
  return TREE_CODE (t) == INTEGER_CST && !TREE_OVERFLOW (t);
}
The patch uses ! modifier to ensure the bswap is simplified and
extends support to GENERIC by means of requiring !EXPR_P which
is not perfect but a conservative approximation.

2022-02-22  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/104644
	* doc/match-and-simplify.texi: Amend ! documentation.
	* genmatch.cc (expr::gen_transform): Code-generate ! support
	for GENERIC.
	(parser::parse_expr): Allow ! for GENERIC.
	* match.pd (cmp (bswap @0) INTEGER_CST@1): Use ! modifier on
	bswap.

	* gcc.dg/pr104644.c: New test.

Co-Authored-by: Jakub Jelinek <jakub@redhat.com>