On 7/8/2026 2:19 AM, Andrew Pinski wrote:
Since match and simplify can add unused statements to the sequence
in some cases, we should remove them before call phiopt_early_allow.
This is needed for 2 future patches. One is to allowing of comparisons,
optionally with a cast and optional with a negative expression.
The other is about supporting a way to handling
cond_removal_in_builtin_zero_pattern in match and also adding a new match
pattern to fix PR 126035 (ctz split back into one).
Bootstrapped and tested on x86_64-linux-gnu.
gcc/ChangeLog:
* tree-ssa-phiopt.cc (remove_unused_stmts): New function.
(gimple_simplify_phiopt): Call remove_unused_stmts before
phiopt_early_allow.
I'm torn. Not particularly happy with what appears to be a mini DCE
pass on the sequence. Presumably the motivation is to clean things up
in a way that makes phiopt_early_allow more likely to return true by
removing statements that are going to be zapped by DCE later and thus
shouldn't participate in phiopt_early_allow?
jeff
