[Bug target/112776] RISC-V Regression: Missed optimization of VSETVL PASS

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112776

--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Lehua Ding <lhtin@gcc.gnu.org>:

https://gcc.gnu.org/g:923a67f17badcbe6e2b2e5d3570a265443258c8e

commit r14-6027-g923a67f17badcbe6e2b2e5d3570a265443258c8e
Author: Juzhe-Zhong <juzhe.zhong@rivai.ai>
Date:   Fri Dec 1 08:39:57 2023 +0800

    RISC-V: Fix VSETVL PASS regression

    This patch fix 2 regression (one is bug regression, the other is
performance regression).
    Those 2 regressions are both we are comparing ratio for same AVL in wrong
place.

    1. BUG regression:
    avl_single-84.c:

    f0:
            li      a5,999424
            add     a1,a1,a5
            li      a4,299008
            add     a5,a0,a5
            addi    a3,a4,992
            addi    a5,a5,576
            addi    a1,a1,576
            vsetvli a4,zero,e8,m2,ta,ma
            add     a0,a0,a3
            vlm.v   v1,0(a5)
            vsm.v   v1,0(a1)
            vl1re64.v       v1,0(a0)
            beq     a2,zero,.L10
            li      a5,0
            vsetvli zero,zero,e64,m1,tu,ma   --->  This is totally incorrect
since the ratio above is 4, wheras it is demanding ratio = 64 here.
    .L3:
            fcvt.d.lu       fa5,a5
            addi    a5,a5,1
            fadd.d  fa5,fa5,fa0
            vfmv.s.f        v1,fa5
            bne     a5,a2,.L3
            vfmv.f.s        fa0,v1
            ret
    .L10:
            vsetvli zero,zero,e64,m1,ta,ma
            vfmv.f.s        fa0,v1
            ret

    2. Performance regression:

    before this patch:

            vsetvli a5,a4,e8,m1,ta,ma
            vsetvli zero,a5,e32,m1,tu,ma
            vmv.s.x v2,zero
            vmv.s.x v1,zero
            vsetvli zero,a5,e32,m4,tu,ma
            vle32.v v4,0(a1)
            vfmul.vv        v4,v4,v4
            vfredosum.vs    v1,v4,v2
            vfmv.f.s        fa5,v1
            fsw     fa5,0(a0)
            sub     a4,a4,a5
            bne     a4,zero,.L2
            ret

    After this patch:

            vsetvli a5,a4,e32,m4,tu,ma
            vle32.v v4,0(a1)
            vmv.s.x v2,zero
            vmv.s.x v1,zero
            vfmul.vv        v4,v4,v4
            vfredosum.vs    v1,v4,v2
            vfmv.f.s        fa5,v1
            fsw     fa5,0(a0)
            sub     a4,a4,a5
            bne     a4,zero,.L2
            ret

    Tested rv64gcv_zvfh_zfh passed no regression.

    zvl256b/zvl512b/zvl1024b/zve64d is runing.

            PR target/112776

    gcc/ChangeLog:

            * config/riscv/riscv-vsetvl.cc
(pre_vsetvl::pre_global_vsetvl_info): Fix ratio.

    gcc/testsuite/ChangeLog:

            * gcc.target/riscv/rvv/vsetvl/avl_single-84.c: Adapt test.
            * gcc.target/riscv/rvv/vsetvl/pr111037-3.c: Ditto.
            * gcc.target/riscv/rvv/vsetvl/pr112776.c: New test.