> On the other hand, even RVA23 is quite poor at signed overflow checking

When I tried to measure the impact of -ftrapv in RVA23 and armv9, it was roughly the same: https://news.ycombinator.com/item?id=46228597#46250569

reminder:

    unsigned 64-bit:
    add: RV: add+bltu       Arm: adds+bcc
    sub: RV: sub+bltu       Arm: subs+bcs
    mul: RV: mulhu+mul+beqz Arm: umulh+mul+cbz
    
    unsigned 32-bit:
    add: RV: addw+bgeu     Arm: adds+bcc
    sub: RV: subw+bgeu     Arm: subs+bcs
    mul: RV: mul+slli+beqz Arm: umul+cmp lsr 32

    signed 64-bit:
    add: RV: add+slt+slti+beq  Arm: adds+bcc
    sub: RV: sub+slt+slti+beq  Arm: subs+bcs
    mul: RV: mulh+mul+srai+beq Arm: smulh+mul+cmp asr 63
    
    signed 32-bit:
    add: RV: addw+add+beq   Arm: adds+bvc
    sub: RV: subw+sub+beq   Arm: subs+bvs
    mul: RV: mul+sext.w+bew Arm: smul+asr+cmp asr 31