-/* Given a set of blocks with variable definitions (DEF_BLOCKS),
- return a bitmap with all the blocks in the iterated dominance
- frontier of the blocks in DEF_BLOCKS. DFS contains dominance
- frontier information as returned by compute_dominance_frontiers.
-
- The resulting set of blocks are the potential sites where PHI nodes
- are needed. The caller is responsible for freeing the memory
- allocated for the return value. */
-
-static bitmap
-compute_idf (bitmap def_blocks, bitmap *dfs)
-{
- bitmap_iterator bi;
- unsigned bb_index, i;
- VEC(int,heap) *work_stack;
- bitmap phi_insertion_points;
-
- work_stack = VEC_alloc (int, heap, n_basic_blocks);
- phi_insertion_points = BITMAP_ALLOC (NULL);
-
- /* Seed the work list with all the blocks in DEF_BLOCKS. We use
- VEC_quick_push here for speed. This is safe because we know that
- the number of definition blocks is no greater than the number of
- basic blocks, which is the initial capacity of WORK_STACK. */
- EXECUTE_IF_SET_IN_BITMAP (def_blocks, 0, bb_index, bi)
- VEC_quick_push (int, work_stack, bb_index);
-
- /* Pop a block off the worklist, add every block that appears in
- the original block's DF that we have not already processed to
- the worklist. Iterate until the worklist is empty. Blocks
- which are added to the worklist are potential sites for
- PHI nodes. */
- while (VEC_length (int, work_stack) > 0)
- {
- bb_index = VEC_pop (int, work_stack);
-
- /* Since the registration of NEW -> OLD name mappings is done
- separately from the call to update_ssa, when updating the SSA
- form, the basic blocks where new and/or old names are defined
- may have disappeared by CFG cleanup calls. In this case,
- we may pull a non-existing block from the work stack. */
- gcc_assert (bb_index < (unsigned) last_basic_block);
-
- EXECUTE_IF_AND_COMPL_IN_BITMAP (dfs[bb_index], phi_insertion_points,
- 0, i, bi)
- {
- /* Use a safe push because if there is a definition of VAR
- in every basic block, then WORK_STACK may eventually have
- more than N_BASIC_BLOCK entries. */
- VEC_safe_push (int, heap, work_stack, i);
- bitmap_set_bit (phi_insertion_points, i);
- }
- }
-
- VEC_free (int, heap, work_stack);
-
- return phi_insertion_points;
-}
-
-