Phi-node Propagation: Skip Clobbers More Effectively
The phi-node propagation pass now skips over clobbering instructions more effectively, improving optimization opportunities.
This commit improves the phi-node propagation pass (phiprop) by enabling it to skip over clobbering instructions more effectively. This allows the pass to propagate values through more complex code sequences. The changes specifically handle cases where aggregates (structures or arrays) are involved, improving the accuracy and effectiveness of the optimization.
In Details
This patch addresses PR116823 by improving clobber handling in tree-ssa-phiprop.cc. The logic in can_handle_load is modified to skip over clobbers, with special handling for aggregates. The patch also includes new test cases to verify aggregate handling.
For Context
Phi-node propagation is an optimization technique used in GCC to simplify code by replacing variables with their known values at certain points in the program. A "phi-node" represents the merging of values from different control flow paths. A "clobber" is an instruction that modifies a variable, potentially invalidating any previously known value. This commit makes the optimization more robust by allowing it to skip over instructions that modify variables, increasing the scope for optimization.