Range Analysis Can Now Mark Statements for Recalculation
The range analysis can now mark statements as stale, forcing recalculation of their value ranges when next used.
This commit introduces a mechanism for the range analysis in GCC to mark statements as stale. When an SSA name is marked as “to be recalculated,” its value range will be recomputed the next time it is used. This allows the range analysis to respond to changes in the code and maintain accurate value ranges, leading to better optimization opportunities.
In Details
This patch introduces a new update_range_info method and a mark_stale function in gimple-range-cache.cc and related headers. The ranger_cache now allocates a bitmap to track stale SSA names. gimple_set_modified is updated to call the new update_range_info variant. These changes allow the range analysis to invalidate cached ranges and trigger recalculation when necessary.
For Context
GCC uses range analysis to track the possible values of variables and expressions. This information is used to perform various optimizations, such as eliminating dead code and simplifying calculations. Sometimes, the compiler needs to update its knowledge about a variable's range. This commit adds a way to mark the information about a value as out-of-date, so that the compiler will recalculate it when needed. This ensures that the range analysis is as accurate as possible, leading to better optimized code.