unchangedIR

unchangedIR is a compiler optimization pass that identifies and preserves parts of the intermediate representation (IR) that have not been modified by previous optimization steps. Its primary goal is to avoid unnecessary recomputation or regeneration of IR code that is already in a satisfactory state. By recognizing unchanged IR, the compiler can focus its resources on the sections that require further processing, potentially leading to faster compilation times and more efficient generated code.

The implementation of unchangedIR typically involves tracking changes made to the IR during optimization passes. When a pass completes, it compares the current state of the IR with its state before the pass. If a particular section of the IR remains unaltered, it can be marked as unchanged. Subsequent passes can then consult these markings to determine whether they need to operate on that section. This can be particularly beneficial in complex compilation pipelines with many optimization stages.

The benefits of unchangedIR include reduced compiler overhead and potentially improved code quality. By not re-optimizing already optimal code, compilers can save computational resources. Furthermore, by preventing unintended modifications to already well-formed IR, it can help maintain the integrity of the code throughout the compilation process. The effectiveness of unchangedIR can depend on the granularity of the IR tracking and the nature of the optimization passes applied.