[Bug target/113112] RISC-V: Dynamic LMUL feature stabilization for GCC-14 release

["cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113112

--- Comment #5 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Pan Li <panli@gcc.gnu.org>:

https://gcc.gnu.org/g:a43bd8255451227fc1cd3601b1f0265b21fafada

commit r14-6889-ga43bd8255451227fc1cd3601b1f0265b21fafada
Author: Juzhe-Zhong <juzhe.zhong@rivai.ai>
Date:   Tue Jan 2 11:37:43 2024 +0800

    RISC-V: Make liveness be aware of rgroup number of LENS[dynamic LMUL]

    This patch fixes the following situation:
    vl4re16.v       v12,0(a5)
    ...
    vl4re16.v       v16,0(a3)
    vs4r.v  v12,0(a5)
    ...
    vl4re16.v       v4,0(a0)
    vs4r.v  v16,0(a3)
    ...
    vsetvli a3,zero,e16,m4,ta,ma
    ...
    vmv.v.x v8,t6
    vmsgeu.vv       v2,v16,v8
    vsub.vv v16,v16,v8
    vs4r.v  v16,0(a5)
    ...
    vs4r.v  v4,0(a0)
    vmsgeu.vv       v1,v4,v8
    ...
    vsub.vv v4,v4,v8
    slli    a6,a4,2
    vs4r.v  v4,0(a5)
    ...
    vsub.vv v4,v12,v8
    vmsgeu.vv       v3,v12,v8
    vs4r.v  v4,0(a5)
    ...

    There are many spills which are 'vs4r.v'.  The root cause is that we don't
count
    vector REG liveness referencing the rgroup controls.

    _29 = _25->iatom[0]; is transformed into the following vect statement with
4 different loop_len (loop_len_74, loop_len_75, loop_len_76, loop_len_77).

      vect__29.11_78 = .MASK_LEN_LOAD (vectp_sb.9_72, 32B, { -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, loop_len_74, 0);
      vect__29.12_80 = .MASK_LEN_LOAD (vectp_sb.9_79, 32B, { -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, loop_len_75, 0);
      vect__29.13_82 = .MASK_LEN_LOAD (vectp_sb.9_81, 32B, { -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, loop_len_76, 0);
      vect__29.14_84 = .MASK_LEN_LOAD (vectp_sb.9_83, 32B, { -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1 }, loop_len_77, 0);

    which are the LENS number (LOOP_VINFO_LENS (loop_vinfo).length ()).

    Count liveness according to LOOP_VINFO_LENS (loop_vinfo).length () to
compute liveness more accurately:

    vsetivli        zero,8,e16,m1,ta,ma
    vmsgeu.vi       v19,v14,8
    vadd.vi v18,v14,-8
    vmsgeu.vi       v17,v1,8
    vadd.vi v16,v1,-8
    vlm.v   v15,0(a5)
    ...

    Tested no regression, ok for trunk ?

            PR target/113112

    gcc/ChangeLog:

            * config/riscv/riscv-vector-costs.cc (compute_nregs_for_mode): Add
rgroup info.
            (max_number_of_live_regs): Ditto.
            (has_unexpected_spills_p): Ditto.

    gcc/testsuite/ChangeLog:

            * gcc.dg/vect/costmodel/riscv/rvv/pr113112-5.c: New test.