Re: [PATCH 02/11] tcg/riscv: Probe for Zba, Zbb, Zicond extensions

[Alistair Francis <alistair23@gmail.com>]

On Wed, May 3, 2023 at 6:59 PM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Define a useful subset of the extensions.  Probe for them
> via compiler pre-processor feature macros and SIGILL.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Acked-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  tcg/riscv/tcg-target.h     |  6 +++
>  tcg/riscv/tcg-target.c.inc | 96 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 102 insertions(+)
>
> diff --git a/tcg/riscv/tcg-target.h b/tcg/riscv/tcg-target.h
> index 494c986b49..863ac8ba2f 100644
> --- a/tcg/riscv/tcg-target.h
> +++ b/tcg/riscv/tcg-target.h
> @@ -90,6 +90,12 @@ typedef enum {
>  #define TCG_TARGET_CALL_ARG_I128        TCG_CALL_ARG_NORMAL
>  #define TCG_TARGET_CALL_RET_I128        TCG_CALL_RET_NORMAL
>
> +#if defined(__riscv_arch_test) && defined(__riscv_zbb)
> +# define have_zbb true
> +#else
> +extern bool have_zbb;
> +#endif
> +
>  /* optional instructions */
>  #define TCG_TARGET_HAS_movcond_i32      0
>  #define TCG_TARGET_HAS_div_i32          1
> diff --git a/tcg/riscv/tcg-target.c.inc b/tcg/riscv/tcg-target.c.inc
> index 4dd33c73e8..49ff9c8b9d 100644
> --- a/tcg/riscv/tcg-target.c.inc
> +++ b/tcg/riscv/tcg-target.c.inc
> @@ -113,6 +113,20 @@ static const int tcg_target_call_iarg_regs[] = {
>      TCG_REG_A7,
>  };
>
> +#ifndef have_zbb
> +bool have_zbb;
> +#endif
> +#if defined(__riscv_arch_test) && defined(__riscv_zba)
> +# define have_zba true
> +#else
> +static bool have_zba;
> +#endif
> +#if defined(__riscv_arch_test) && defined(__riscv_zicond)
> +# define have_zicond true
> +#else
> +static bool have_zicond;
> +#endif
> +
>  static TCGReg tcg_target_call_oarg_reg(TCGCallReturnKind kind, int slot)
>  {
>      tcg_debug_assert(kind == TCG_CALL_RET_NORMAL);
> @@ -234,6 +248,34 @@ typedef enum {
>
>      OPC_FENCE = 0x0000000f,
>      OPC_NOP   = OPC_ADDI,   /* nop = addi r0,r0,0 */
> +
> +    /* Zba: Bit manipulation extension, address generation */
> +    OPC_ADD_UW = 0x0800003b,
> +
> +    /* Zbb: Bit manipulation extension, basic bit manipulaton */
> +    OPC_ANDN   = 0x40007033,
> +    OPC_CLZ    = 0x60001013,
> +    OPC_CLZW   = 0x6000101b,
> +    OPC_CPOP   = 0x60201013,
> +    OPC_CPOPW  = 0x6020101b,
> +    OPC_CTZ    = 0x60101013,
> +    OPC_CTZW   = 0x6010101b,
> +    OPC_ORN    = 0x40006033,
> +    OPC_REV8   = 0x6b805013,
> +    OPC_ROL    = 0x60001033,
> +    OPC_ROLW   = 0x6000103b,
> +    OPC_ROR    = 0x60005033,
> +    OPC_RORW   = 0x6000503b,
> +    OPC_RORI   = 0x60005013,
> +    OPC_RORIW  = 0x6000501b,
> +    OPC_SEXT_B = 0x60401013,
> +    OPC_SEXT_H = 0x60501013,
> +    OPC_XNOR   = 0x40004033,
> +    OPC_ZEXT_H = 0x0800403b,
> +
> +    /* Zicond: integer conditional operations */
> +    OPC_CZERO_EQZ = 0x0e005033,
> +    OPC_CZERO_NEZ = 0x0e007033,
>  } RISCVInsn;
>
>  /*
> @@ -1612,8 +1654,62 @@ static void tcg_target_qemu_prologue(TCGContext *s)
>      tcg_out_opc_imm(s, OPC_JALR, TCG_REG_ZERO, TCG_REG_RA, 0);
>  }
>
> +static volatile sig_atomic_t got_sigill;
> +
> +static void sigill_handler(int signo, siginfo_t *si, void *data)
> +{
> +    /* Skip the faulty instruction */
> +    ucontext_t *uc = (ucontext_t *)data;
> +    uc->uc_mcontext.__gregs[REG_PC] += 4;
> +
> +    got_sigill = 1;
> +}
> +
> +static void tcg_target_detect_isa(void)
> +{
> +#if !defined(have_zba) || !defined(have_zbb) || !defined(have_zicond)
> +    /*
> +     * TODO: It is expected that this will be determinable via
> +     * linux riscv_hwprobe syscall, not yet merged.
> +     * In the meantime, test via sigill.
> +     */
> +
> +    struct sigaction sa_old, sa_new;
> +
> +    memset(&sa_new, 0, sizeof(sa_new));
> +    sa_new.sa_flags = SA_SIGINFO;
> +    sa_new.sa_sigaction = sigill_handler;
> +    sigaction(SIGILL, &sa_new, &sa_old);
> +
> +#ifndef have_zba
> +    /* Probe for Zba: add.uw zero,zero,zero. */
> +    got_sigill = 0;
> +    asm volatile(".insn %0" : : "i"(OPC_ADD_UW) : "memory");
> +    have_zba = !got_sigill;
> +#endif
> +
> +#ifndef have_zbb
> +    /* Probe for Zba: andn zero,zero,zero. */
> +    got_sigill = 0;
> +    asm volatile(".insn %0" : : "i"(OPC_ANDN) : "memory");
> +    have_zbb = !got_sigill;
> +#endif
> +
> +#ifndef have_zicond
> +    /* Probe for Zicond: czero.eqz zero,zero,zero. */
> +    got_sigill = 0;
> +    asm volatile(".insn %0" : : "i"(OPC_CZERO_EQZ) : "memory");
> +    have_zicond = !got_sigill;
> +#endif
> +
> +    sigaction(SIGILL, &sa_old, NULL);
> +#endif
> +}
> +
>  static void tcg_target_init(TCGContext *s)
>  {
> +    tcg_target_detect_isa();
> +
>      tcg_target_available_regs[TCG_TYPE_I32] = 0xffffffff;
>      tcg_target_available_regs[TCG_TYPE_I64] = 0xffffffff;
>
> --
> 2.34.1
>
>