https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127547
--- Comment #2 from Peter Bergner <bergner at gcc dot gnu.org> --- My git bisect identified the following as the culprit commit: commit 0b67b93cfe0 [r17-3908-g0b67b93cfe0a67] Author: Robin Dapp <[email protected]> AuthorDate: Mon Aug 31 14:42:10 2026 +0200 Commit: Robin Dapp <[email protected]> CommitDate: Thu Sep 3 23:10:55 2026 +0200 RISC-V: Set REGMODE_NATURAL_SIZE for VLS vectors. Following the middle-end changes, this patch makes REGMODE_NATURAL_SIZE return the size of one vector. This implies that subregs of VLS vectors smaller than the vector itself are invalid. Note that this is going to cause a few code-quality regression. Before this change, we could rely on "subregging" our way into vectors but that's not possible anymore. My plan is to fix this by a few adjustments to vec-vec extracts and vec-vec sets during expand, defining a vec-vec vec_init for riscv, as well maybe adding vec_extract and vec_set rtx codes to help with all of that.
