Phirop: Move the VUSE check before dominator tests.
The VUSE check now happens before the dominator tests in the phiprop pass, which should result in a small optimization.
The phiprop pass now performs the VUSE check before the dominator tests. This reordering avoids unnecessary dominator tests when the VUSE check would have failed, resulting in a small optimization. The dominator tests no longer indicate if a propagation can occur, so checks that prevent propagation should be performed first.
In Details
The commit reorders checks within propagate_with_phi in tree-ssa-phiprop.cc. Moving the VUSE check before dominator tests avoids unnecessary computation when the VUSE check fails. The dominator tests do not determine if a propagation will occur, so checks that prevent propagation are performed first.
For Context
The phiprop pass in GCC optimizes code by propagating values through phi nodes (used to merge values from different control flow paths). This commit reorders the checks performed during this propagation process. Specifically, a check related to 'VUSE' (likely a check related to variable usage) is now performed before 'dominator tests' (which determine if one block of code always executes before another). This optimization avoids unnecessary work when the VUSE check would have failed.