https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119103
--- Comment #17 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Biener <rgue...@gcc.gnu.org>: https://gcc.gnu.org/g:6901d56fea2132389e9a7ae60b4d9731e6e3c65a commit r16-190-g6901d56fea2132389e9a7ae60b4d9731e6e3c65a Author: Richard Biener <rguent...@suse.de> Date: Tue Mar 4 10:34:39 2025 +0100 tree-optimization/119103 - missed overwidening detection for shift When vectorizing a shift of u16 data by an amount that's known to be less than 16 we currently fail to emit a vector u16 shift. The first reason is that the promotion of the shift amount is hoisted only by PRE and that cannot preserve range info, the second reason is that pattern detection doesn't use range info when computing the precision required for an operation. The following addresses the first issue by making LIM hoist all expressions for the pass that runs right before PRE and the second issue by querying ranges for the shift amount. PR tree-optimization/119103 * tree-ssa-loop-im.cc (in_loop_pipeline): Globalize. (compute_invariantness): Override costing when we run right before PRE and PRE is enabled. (pass_lim::execute): Adjust. * tree-vect-patterns.cc (vect_determine_precisions_from_users): For variable shift amounts use range information. * gcc.target/i386/pr119103.c: New testcase.
