GNU Compiler Collection (GCC) Internals: Statement and operand traversals

GNU Compiler Collection (GCC) Internals: Statement and operand traversals

11.12 Statement and operand traversals

There are two functions available for walking statements and sequences: walk_gimple_stmt and walk_gimple_seq, accordingly, and a third function for walking the operands in a statement: walk_gimple_op.

GIMPLE function: tree walk_gimple_stmt (gimple_stmt_iterator *gsi, walk_stmt_fn callback_stmt, walk_tree_fn callback_op, struct walk_stmt_info *wi)

This function is used to walk the current statement in GSI, optionally using traversal state stored in WI. If WI is NULL, no state is kept during the traversal.

The callback CALLBACK_STMT is called. If CALLBACK_STMT returns true, it means that the callback function has handled all the operands of the statement and it is not necessary to walk its operands.

If CALLBACK_STMT is NULL or it returns false, CALLBACK_OP is called on each operand of the statement via walk_gimple_op. If walk_gimple_op returns non-NULL for any operand, the remaining operands are not scanned.

The return value is that returned by the last call to walk_gimple_op, or NULL_TREE if no CALLBACK_OP is specified.

GIMPLE function: tree walk_gimple_op (gimple stmt, walk_tree_fn callback_op, struct walk_stmt_info *wi)

Use this function to walk the operands of statement STMT. Every operand is walked via walk_tree with optional state information in WI.

CALLBACK_OP is called on each operand of STMT via walk_tree. Additional parameters to walk_tree must be stored in WI. For each operand OP, walk_tree is called as:

walk_tree (&OP, CALLBACK_OP, WI, PSET)

If CALLBACK_OP returns non-NULL for an operand, the remaining operands are not scanned. The return value is that returned by the last call to walk_tree, or NULL_TREE if no CALLBACK_OP is specified.

GIMPLE function: tree walk_gimple_seq (gimple_seq seq, walk_stmt_fn callback_stmt, walk_tree_fn callback_op, struct walk_stmt_info *wi): This function walks all the statements in the sequence SEQ calling walk_gimple_stmt on each one. WI is as in walk_gimple_stmt. If walk_gimple_stmt returns non-NULL, the walk is stopped and the value returned. Otherwise, all the statements are walked and NULL_TREE returned.