simplify-rtx: Avoid -Wuninitialized false positive
Fixes a false positive -Wuninitialized warning during profiled bootstraps by improving analysis of conditional initializations.
This commit resolves a false positive -Wuninitialized warning that occurred during profiled bootstraps in GCC’s simplify-rtx pass. The warning stemmed from the compiler’s analyzer failing to recognize that a variable foo would be initialized if a specific condition (is_a <.., &foo>) passed. The fix rewrites the check to avoid an out-parameter, thus eliminating the spurious warning.
In Details
In simplify-context::simplify_subreg, a is_a<..>(&foo) check was triggering a false positive for -Wuninitialized. The analyzer could not deduce that foo would be initialized post-check. The fix avoids passing foo by reference to is_a, removing the problematic aliasing that confused the analyzer.
- simplify-rtx
- A GCC optimization pass that simplifies the compiler's internal representation (RTX) to facilitate further optimizations and code generation.
- profiled bootstrap
- A multi-stage compilation process where the compiler's performance is measured and used to optimize subsequent compilation stages, often used to improve overall compiler speed.
- -Wuninitialized
- A compiler warning flag that detects the use of uninitialized variables, helping to prevent bugs and undefined behavior.
- RTX
- Representation of intermediate code in GCC, used after the front-end parses the source code and before code generation.