https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122216
--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Christophe Lyon <[email protected]>: https://gcc.gnu.org/g:e359564db3ed1826931720aad7c977e1eed9c04c commit r16-5269-ge359564db3ed1826931720aad7c977e1eed9c04c Author: Christophe Lyon <[email protected]> Date: Thu Sep 18 16:41:19 2025 +0000 arm: add support for out of range shift amount in MVE asrl and lsll [PR122216] MVE asrl and lsll instructions have two variants: - immediate shift amount in the [1..32] range - shift amount in a register, where negative values reverse the direction of the shift However, RTL assumes that the shift amount is interpreted unsigned, so we want to make sure undesired simplifications do not take place. For instance if simplify_rtx optimizes (set (reg:SI 1) (const_int -5)) (set (reg:DI 2) (ashift:DI (reg:DI 3) (reg:SI 1))) into: (set (reg:DI 2) (ashift:DI (reg:DI 3) (const_int -5))) we do not want this to be interpreted as undefined behavior. We handle this using a general pattern where: - immediates are handled by a define_insn_and_split pattern which directly maps immediates in [1..32] to the shift operator and splits other cases as needed. - non-immediates are handled by another pattern gcc/ChangeLog: PR target/122216 * config/arm/arm.md (ashldi3, ashrdi3): Force shift amount into QImode. * config/arm/constraints.md: Fix comment, Pg is valid in Thumb-2 state only. * config/arm/mve.md (mve_asrl): Handle various shift amount ranges. (mve_asrl_imm, mve_asrl_internal): New patterns. (mve_lsll): Handle various shift amount ranges. (mve_lsll_imm, mve_lsll_internal): New patterns. gcc/testsuite/ChangeLog: PR target/122216 * gcc.target/arm/mve/intrinsics/asrl-various-ranges.c: New test. * gcc.target/arm/mve/intrinsics/lsll-various-ranges.c: New test.
