https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83907
--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sa...@gcc.gnu.org>: https://gcc.gnu.org/g:1fe04c497d5a16baee6af48a0b08ca99b75724e4 commit r13-455-g1fe04c497d5a16baee6af48a0b08ca99b75724e4 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Fri May 13 22:20:16 2022 +0100 PR tree-optimization/83907: Improved memset handling in strlen pass. This patch implements the missed optimization enhancement PR 83907, by handling memset with a constant byte value in tree-ssa's strlen optimization pass. Effectively, this treats memset(dst,'x',3) as it would memcpy(dst,"xxx",3). This patch also includes a tweak to handle_store to address another missed optimization observed in the related test case pr83907-2.c. The consecutive byte stores to memory get coalesced into a vector write of a vector const, but unfortunately tree-ssa-strlen's handle_store didn't previously handle the (unusual) case where the stored "string" starts with a zero byte but also contains non-zero bytes. 2022-05-13 Roger Sayle <ro...@nextmovesoftware.com> gcc/ChangeLog PR tree-optimization/83907 * tree-ssa-strlen.cc (handle_builtin_memset): Record a strinfo for memset with an constant char value. (handle_store): Improved handling of stores with a first byte of zero, but not storing_all_zeros_p. gcc/testsuite/ChangeLog PR tree-optimization/83907 * gcc.dg/tree-ssa/pr83907-1.c: New test case. * gcc.dg/tree-ssa/pr83907-2.c: New test case.
