Re: [Qemu-devel] [PATCH v8 05/37] target/mips: Add support for emulation of CRC32 group of instructions

[Aleksandar Markovic]

On Monday, August 19, 2019, Aleksandar Markovic <address@hidden> wrote:
> From: Yongbok Kim <address@hidden>
>
> Add emulation of MIPS' CRC32 (Cyclic Redundancy Check) instructions.
> Reuse zlib crc32() and Linux crc32c(). Note that, at the time being,
> there is no MIPS CPU that supports CRC32 instructions (they are an
> optional part of MIPS64/32 R6 anf nanoMIPS ISAs).
>
> Signed-off-by: Yongbok Kim <address@hidden>
> Signed-off-by: Aleksandar Markovic <address@hidden>
> ---
>  disas/mips.c            |  8 ++++++++
>  target/mips/helper.h    |  2 ++
>  target/mips/op_helper.c | 22 ++++++++++++++++++++++
>  target/mips/translate.c | 41 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 73 insertions(+)

This solution is not optimal (see arm equivalent). Also, support for nanomips crc instructions is not included. In spite of that:

Reviewed-by: Aleksandar Markovic <address@hidden>

All outstanding issues will be handled post-4.2.

> diff --git a/disas/mips.c b/disas/mips.c
> index c3a3059..b9a5204 100644
> --- a/disas/mips.c
> +++ b/disas/mips.c
> @@ -1411,6 +1411,14 @@ const struct mips_opcode mips_builtin_opcodes[] =
>  {"evp",        "t",     0x41600004, 0xffe0ffff, TRAP|WR_t,            0, I32R6},
>  {"ginvi",      "v",     0x7c00003d, 0xfc1ffcff, TRAP | INSN_TLB,      0, I32R6},
>  {"ginvt",      "v",     0x7c0000bd, 0xfc1ffcff, TRAP | INSN_TLB,      0, I32R6},
> +{"crc32b",     "t,v,t", 0x7c00000f, 0xfc00ff3f, WR_d | RD_s | RD_t,   0, I32R6},
> +{"crc32h",     "t,v,t", 0x7c00004f, 0xfc00ff3f, WR_d | RD_s | RD_t,   0, I32R6},
> +{"crc32w",     "t,v,t", 0x7c00008f, 0xfc00ff3f, WR_d | RD_s | RD_t,   0, I32R6},
> +{"crc32d",     "t,v,t", 0x7c0000cf, 0xfc00ff3f, WR_d | RD_s | RD_t,   0, I64R6},
> +{"crc32cb",    "t,v,t", 0x7c00010f, 0xfc00ff3f, WR_d | RD_s | RD_t,   0, I32R6},
> +{"crc32ch",    "t,v,t", 0x7c00014f, 0xfc00ff3f, WR_d | RD_s | RD_t,   0, I32R6},
> +{"crc32cw",    "t,v,t", 0x7c00018f, 0xfc00ff3f, WR_d | RD_s | RD_t,   0, I32R6},
> +{"crc32cd",    "t,v,t", 0x7c0001cf, 0xfc00ff3f, WR_d | RD_s | RD_t,   0, I64R6},
>
>  /* MSA */
>  {"sll.b",   "+d,+e,+f", 0x7800000d, 0xffe0003f, WR_VD|RD_VS|RD_VT,  0, MSA},
> diff --git a/target/mips/helper.h b/target/mips/helper.h
> index c7d35bd..0e61043 100644
> --- a/target/mips/helper.h
> +++ b/target/mips/helper.h
> @@ -40,6 +40,8 @@ DEF_HELPER_FLAGS_1(bitswap, TCG_CALL_NO_RWG_SE, tl, tl)
>  DEF_HELPER_FLAGS_1(dbitswap, TCG_CALL_NO_RWG_SE, tl, tl)
>  #endif
>
> +DEF_HELPER_3(crc32, tl, tl, tl, i32)
> +DEF_HELPER_3(crc32c, tl, tl, tl, i32)
>  DEF_HELPER_FLAGS_4(rotx, TCG_CALL_NO_RWG_SE, tl, tl, i32, i32, i32)
>
>  #ifndef CONFIG_USER_ONLY
> diff --git a/target/mips/op_helper.c b/target/mips/op_helper.c
> index 3104904..5874029 100644
> --- a/target/mips/op_helper.c
> +++ b/target/mips/op_helper.c
> @@ -25,6 +25,8 @@
>  #include "exec/exec-all.h"
>  #include "exec/cpu_ldst.h"
>  #include "sysemu/kvm.h"
> +#include "qemu/crc32c.h"
> +#include <zlib.h>
>
>  /*****************************************************************************/
>  /* Exceptions processing helpers */
> @@ -343,6 +345,26 @@ target_ulong helper_rotx(target_ulong rs, uint32_t shift, uint32_t shiftx,
>      return (int64_t)(int32_t)(uint32_t)tmp5;
>  }
>
> +/* these crc32 functions are based on target/arm/helper-a64.c */
> +target_ulong helper_crc32(target_ulong val, target_ulong m, uint32_t sz)
> +{
> +    uint8_t buf[8];
> +    target_ulong mask = ((sz * 8) == 64) ? -1ULL : ((1ULL << (sz * 8)) - 1);
> +
> +    m &= mask;
> +    stq_le_p(buf, m);
> +    return (int32_t) (crc32(val ^ 0xffffffff, buf, sz) ^ 0xffffffff);
> +}
> +
> +target_ulong helper_crc32c(target_ulong val, target_ulong m, uint32_t sz)
> +{
> +    uint8_t buf[8];
> +    target_ulong mask = ((sz * 8) == 64) ? -1ULL : ((1ULL << (sz * 8)) - 1);
> +    m &= mask;
> +    stq_le_p(buf, m);
> +    return (int32_t) (crc32c(val, buf, sz) ^ 0xffffffff);
> +}
> +
>  #ifndef CONFIG_USER_ONLY
>
>  static inline hwaddr do_translate_address(CPUMIPSState *env,
> diff --git a/target/mips/translate.c b/target/mips/translate.c
> index 3f73be0..3f9f113 100644
> --- a/target/mips/translate.c
> +++ b/target/mips/translate.c
> @@ -452,6 +452,7 @@ enum {
>      OPC_LWE            = 0x2F | OPC_SPECIAL3,
>
>      /* R6 */
> +    OPC_CRC32          = 0x0F | OPC_SPECIAL3,
>      R6_OPC_PREF        = 0x35 | OPC_SPECIAL3,
>      R6_OPC_CACHE       = 0x25 | OPC_SPECIAL3,
>      R6_OPC_LL          = 0x36 | OPC_SPECIAL3,
> @@ -2550,6 +2551,7 @@ typedef struct DisasContext {
>      bool saar;
>      bool mi;
>      int gi;
> +    bool crcp;
>  } DisasContext;
>
>  #define DISAS_STOP       DISAS_TARGET_0
> @@ -27041,6 +27043,33 @@ static void decode_opc_special2_legacy(CPUMIPSState *env, DisasContext *ctx)
>      }
>  }
>
> +static void gen_crc32(DisasContext *ctx, int rd, int rs, int rt, int sz,
> +                      int crc32c)
> +{
> +    TCGv t0;
> +    TCGv t1;
> +    TCGv_i32 tsz = tcg_const_i32(1 << sz);
> +    if (rd == 0) {
> +        /* Treat as NOP. */
> +        return;
> +    }
> +    t0 = tcg_temp_new();
> +    t1 = tcg_temp_new();
> +
> +    gen_load_gpr(t0, rt);
> +    gen_load_gpr(t1, rs);
> +
> +    if (crc32c) {
> +        gen_helper_crc32c(cpu_gpr[rd], t0, t1, tsz);
> +    } else {
> +        gen_helper_crc32(cpu_gpr[rd], t0, t1, tsz);
> +    }
> +
> +    tcg_temp_free(t0);
> +    tcg_temp_free(t1);
> +    tcg_temp_free_i32(tsz);
> +}
> +
>  static void decode_opc_special3_r6(CPUMIPSState *env, DisasContext *ctx)
>  {
>      int rs, rt, rd, sa;
> @@ -27055,6 +27084,17 @@ static void decode_opc_special3_r6(CPUMIPSState *env, DisasContext *ctx)
>
>      op1 = MASK_SPECIAL3(ctx->opcode);
>      switch (op1) {
> +    case OPC_CRC32:
> +        if (unlikely(!ctx->crcp) ||
> +            unlikely((extract32(ctx->opcode, 6, 2) == 3) &&
> +                     (!(ctx->hflags & MIPS_HFLAG_64))) ||
> +            unlikely((extract32(ctx->opcode, 8, 3) >= 2))) {
> +            generate_exception_end(ctx, EXCP_RI);
> +        }
> +        gen_crc32(ctx, rt, rs, rt,
> +                  extract32(ctx->opcode, 6, 2),
> +                  extract32(ctx->opcode, 8, 3));
> +        break;
>      case R6_OPC_PREF:
>          if (rt >= 24) {
>              /* hint codes 24-31 are reserved and signal RI */
> @@ -30049,6 +30089,7 @@ static void mips_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
>      ctx->abs2008 = (env->active_fpu.fcr31 >> FCR31_ABS2008) & 1;
>      ctx->mi = (env->CP0_Config5 >> CP0C5_MI) & 1;
>      ctx->gi = (env->CP0_Config5 >> CP0C5_GI) & 3;
> +    ctx->crcp = (env->CP0_Config5 >> CP0C5_CRCP) & 1;
>      restore_cpu_state(env, ctx);
>  #ifdef CONFIG_USER_ONLY
>          ctx->mem_idx = MIPS_HFLAG_UM;
> -- 
> 2.7.4