WALK_DATA->GLOBAL_DATA->KILLS.
2- If S uses a variable VAR and there is no preceding kill of VAR,
- then it is marked in marked in the LIVEIN_BLOCKS bitmap
- associated with VAR.
+ then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
This information is used to determine which variables are live
across block boundaries to reduce the number of PHI nodes
4- Rename all the blocks (rewrite_blocks) and statements in the program.
- Steps 3 and 5 are done using the dominator tree walker
+ Steps 3 and 4 are done using the dominator tree walker
(walk_dominator_tree). */
static void