Shrink back size of tree_exp from 40 bytes to 32

The following patch implements what I've mentioned in the 64-bit
location_t thread.
struct tree_exp had unsigned condition_uid member added for something
rarely used (-fcondition-coverage) and even there used only on very small
subset of trees only for the duration of the gimplification.

The following patch uses a hash_map instead, which allows shrinking
tree_exp to its previous size (32 bytes + (number of operands - 1) * sizeof
(tree)).

2024-12-15  Jakub Jelinek  <jakub@redhat.com>

	* tree-core.h (struct tree_exp): Remove condition_uid member.
	* tree.h (SET_EXPR_UID, EXPR_COND_UID): Remove.
	* gimplify.cc (nextuid): Rename to ...
	(nextconduid): ... this.
	(cond_uids): New static variable.
	(next_cond_uid, reset_cond_uid): Adjust for the renaming,
	formatting fix.
	(tree_associate_condition_with_expr): New function.
	(shortcut_cond_r, tag_shortcut_cond, shortcut_cond_expr): Use it
	instead of SET_EXPR_UID.
	(gimplify_cond_expr): Look up cond_uid in cond_uids hash map if
	non-NULL instead of using EXPR_COND_UID.
	(gimplify_function_tree): Delete cond_uids and set it to NULL.