[Bug tree-optimization/122635] RISC-V: -mrvv-vector-bits=zvl introducing unoptimal vsetivli zero,0 and insns depending on AVL nops

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122635

--- Comment #21 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Robin Dapp <rdapp@gcc.gnu.org>:

https://gcc.gnu.org/g:cee0a9dd2700b9adff64b2d7e1f222671b1b2058

commit r16-5984-gcee0a9dd2700b9adff64b2d7e1f222671b1b2058
Author: Robin Dapp <rdapp@ventanamicro.com>
Date:   Tue Nov 25 10:34:55 2025 +0100

    fold: Elide MASK_LEN_LOAD/STORE with zero length [PR122635].

    This patch adds zero-length handling to gimple_fold_partial_store and
    gimple_fold_partial_load and unifies them into
    gimple_fold_partial_load_store.

    It introduces a new function partial_load_store_mask_state that
    returns
     MASK_ALL_INACTIVE,
     MASK_ALL_ACTIVE, or
     MASK_UNKNOWN.

    This result is used to either replace a load with its else value and
    elide a store (when all inactive), turn the load/store into a regular
    mem ref (all_active), or do nothing.

            PR tree-optimization/122635

    gcc/ChangeLog:

            * gimple-fold.cc (enum mask_load_store_state): New enum.
            (gimple_fold_partial_load_store_mem_ref): Only fold
            "all active" loads/stores.
            (partial_load_store_mask_state): New function to compute mask
            state.
            (gimple_fold_partial_load): Remove.
            (gimple_fold_partial_load_store): New function.
            (gimple_fold_partial_store): Remove.
            (gimple_fold_call): Use new function.

    gcc/testsuite/ChangeLog:

            * gcc.target/aarch64/sve/pfalse-store.c: Expect more elided
            stores.
            * gcc.target/riscv/rvv/autovec/pr122635-1.c: New test.
            * gcc.target/riscv/rvv/autovec/pr122635-2.c: New test.
            * gcc.target/powerpc/p9-vec-length-epil-8.c: Expect two lxvl
            less.