tree-object-size: Support dynamic sizes in conditions

tree-object-size: Support dynamic sizes in conditions

Handle GIMPLE_PHI and conditionals specially for dynamic objects,
returning PHI/conditional expressions instead of just a MIN/MAX
estimate.

This makes the returned object size variable for loops and conditionals,
so tests need to be adjusted to look for precise size in some cases.
builtin-dynamic-object-size-5.c had to be modified to only look for
success in maximum object size case and skip over the minimum object
size tests because the result is no longer a compile time constant.

I also added some simple tests to exercise conditionals with dynamic
object sizes.

gcc/ChangeLog:

	PR middle-end/70090
	* builtins.c (fold_builtin_object_size): Adjust for dynamic size
	expressions.
	* tree-object-size.c: Include gimplify-me.h.
	(struct object_size_info): New member UNKNOWNS.
	(size_initval_p, size_usable_p, object_sizes_get_raw): New
	functions.
	(object_sizes_get): Return suitable gimple variable for
	object size.
	(bundle_sizes): New function.
	(object_sizes_set): Use it and handle dynamic object size
	expressions.
	(object_sizes_set_temp): New function.
	(size_for_offset): Adjust for dynamic size expressions.
	(emit_phi_nodes, propagate_unknowns, gimplify_size_expressions):
	New functions.
	(compute_builtin_object_size): Call gimplify_size_expressions
	for OST_DYNAMIC.
	(dynamic_object_size): New function.
	(cond_expr_object_size): Use it.
	(phi_dynamic_object_size): New function.
	(collect_object_sizes_for): Call it for OST_DYNAMIC.  Adjust to
	accommodate dynamic object sizes.

gcc/testsuite/ChangeLog:

	PR middle-end/70090
	* gcc.dg/builtin-dynamic-object-size-0.c: New tests.
	* gcc.dg/builtin-dynamic-object-size-10.c: Add comment.
	* gcc.dg/builtin-dynamic-object-size-5-main.c: New file.
	* gcc.dg/builtin-dynamic-object-size-5.c: Use it and change test
	to dg-do run.
	* gcc.dg/builtin-object-size-5.c [!N]: Define N.
	(test1, test2, test3, test4) [__builtin_object_size]: Expect
	exact result for __builtin_dynamic_object_size.
	* gcc.dg/builtin-object-size-1.c [__builtin_object_size]: Expect
	exact size expressions for __builtin_dynamic_object_size.
	* gcc.dg/builtin-object-size-2.c [__builtin_object_size]:
	Likewise.
	* gcc.dg/builtin-object-size-3.c [__builtin_object_size]:
	Likewise.
	* gcc.dg/builtin-object-size-4.c [__builtin_object_size]:
	Likewise.

Signed-off-by: Siddhesh Poyarekar <siddhesh@gotplt.org>