MATCH: Simplify zero/sign extension bit operations [PR122848]
MATCH patterns now simplify bitwise operations involving zero and sign extensions of the same value.
The GCC MATCH (Machine Architecture Tree Transformation) system has gained new patterns to simplify bitwise operations on values that have undergone both zero and sign extensions. Specifically, it now folds (zero_extend & sign_extend) to yield the zero_extend result, and (zero_extend | sign_extend) to yield the sign_extend result. This optimization flattens redundant operations, potentially leading to more efficient machine code and has been validated with a new test case for PR122848.
In Details
The MATCH optimization framework has new patterns in match.pd to fold bitwise operations involving zero and sign extensions from the same low-precision value. Specifically, (zero_extend & sign_extend) is folded to zero_extend, and (zero_extend | sign_extend) is folded to sign_extend. This addresses PR122848.
- MATCH
- A framework within GCC used for defining and applying machine-specific or generic tree-based optimizations.
- zero extension
- An operation that extends a smaller integer type to a larger one by appending bits, filling the most significant bits with zeros.
- sign extension
- An operation that extends a smaller integer type to a larger one by replicating the most significant bit (the sign bit) into the newly added higher-order bits.
- fold
- An optimization where a complex expression is replaced by a simpler, equivalent one.
- bitwise operations
- Operations that manipulate individual bits of data, such as AND, OR, XOR.
- PR122848
- A Problem Report number in GCC's bug tracking system, referencing a specific issue that this commit addresses.