[Bug target/115703] [15 Regression] rv64gcv_zvl256b miscompile since r15-1579-g792f97b44ff

[rdapp at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115703

--- Comment #4 from Robin Dapp <rdapp at gcc dot gnu.org> ---
The problem appears to be

    Fuse curr info since prev info compatible with it:
      prev_info: VALID (insn 438, bb 2)
        Demand fields: demand_ge_sew demand_non_zero_avl
        SEW=32, VLMUL=m1, RATIO=32, MAX_SEW=64
        TAIL_POLICY=agnostic, MASK_POLICY=agnostic
        AVL=(reg:DI 0 zero)
        VL=(reg:DI 9 s1 [312])
      curr_info: VALID (insn 92, bb 20)
        Demand fields: demand_ratio_and_ge_sew demand_avl
        SEW=64, VLMUL=m1, RATIO=64, MAX_SEW=64
        TAIL_POLICY=agnostic, MASK_POLICY=agnostic
        AVL=(const_int 4 [0x4])
        VL=(nil)
      prev_info after fused: VALID (insn 438, bb 2)
        Demand fields: demand_ratio_and_ge_sew demand_avl
        SEW=64, VLMUL=mf2, RATIO=64, MAX_SEW=64
        TAIL_POLICY=agnostic, MASK_POLICY=agnostic
        AVL=(const_int 4 [0x4])
        VL=(nil)

where we fuse

vsetvl ...,e32,m1

and

vsetvl ...,e64,m1

to

vsetvl ...,e64,mf2

Testing a patch.