anonymous_namespace{common_subexpression_elimination.cc} Namespace Reference

Functions
Item *	OrGroupWithSomeRemoved (Item_cond_or *or_item, const List< Item > &items_to_remove)
	For an OR disjunction, return a new disjunction with elements from “items_to_remove” logically set to TRUE (ie., removed). More...
bool	IsOr (const Item *item)
bool	AlwaysPresent (Item *expr, const Item *item)
	Check if “item” is necessary to make the expression true. More...
bool	MatchesAny (Item *item, const List< Item > &items)
	Check if “item” matches any item in “items”. More...
void	ExtractItemsExceptSome (Item_cond_and *and_item, const List< Item > &items_to_remove, List< Item > *output)
	For all items in an AND conjunction, add those (possibly none) that are not in “items_to_remove”. More...

Function Documentation

AlwaysPresent()

bool anonymous_namespace{common_subexpression_elimination.cc}::AlwaysPresent	(	Item *	expr,
		const Item *	item
	)

Check if “item” is necessary to make the expression true.

This is case if “expr” is either:

• The same as “item”, or
• (something necessary) OR (something necessary)
• (something necessary) AND anything

A typical case would be of the latter would be

(item AND x) OR (item AND y) OR (z AND w AND item)

ExtractItemsExceptSome()

void anonymous_namespace{common_subexpression_elimination.cc}::ExtractItemsExceptSome	(	Item_cond_and *	and_item,
		const List< Item > &	items_to_remove,
		List< Item > *	output
	)

For all items in an AND conjunction, add those (possibly none) that are not in “items_to_remove”.

E.g., for a AND b AND c, and items_to_remove=(b), adds a and c to “output”.

IsOr()

bool anonymous_namespace{common_subexpression_elimination.cc}::IsOr

(

const Item *

item

)

MatchesAny()

bool anonymous_namespace{common_subexpression_elimination.cc}::MatchesAny	(	Item *	item,
		const List< Item > &	items
	)

Check if “item” matches any item in “items”.

OrGroupWithSomeRemoved()

Item *anonymous_namespace common_subexpression_elimination anonymous_namespace{common_subexpression_elimination.cc}::cc::OrGroupWithSomeRemoved	(	Item_cond_or *	or_item,
		const List< Item > &	items_to_remove
	)

For an OR disjunction, return a new disjunction with elements from “items_to_remove” logically set to TRUE (ie., removed).

If any of the AND-within-OR groups become empty, the expression is always true and nullptr is returned. E.g.:

(a AND b) OR (c AND d), remove (b) => a OR (c AND d) (a AND b) OR (c AND d), remove (b,c) => a OR d (a AND b) OR (c AND d), remove (a,b) => nullptr