Re: [PATCH v2 3/7] tcg/ppc: Use prefixed instructions in tcg_out_mem_long

["Nicholas Piggin" <npiggin@gmail.com>]

On Tue Aug 8, 2023 at 1:02 PM AEST, Richard Henderson wrote:
> When the offset is out of range of the non-prefixed insn, but
> fits the 34-bit immediate of the prefixed insn, use that.
>

The switch will fall through in some cases (at least opi == 0).
Should it have a default: break; to make that obvious?

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> Reviewed-by: Jordan Niethe <jniethe5@gmail.com>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  tcg/ppc/tcg-target.c.inc | 66 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 66 insertions(+)
>
> diff --git a/tcg/ppc/tcg-target.c.inc b/tcg/ppc/tcg-target.c.inc
> index 2141c0bc78..61ae9d8ab7 100644
> --- a/tcg/ppc/tcg-target.c.inc
> +++ b/tcg/ppc/tcg-target.c.inc
> @@ -323,6 +323,15 @@ static bool tcg_target_const_match(int64_t val, TCGType type, int ct)
>  #define STDX   XO31(149)
>  #define STQ    XO62(  2)
>  
> +#define PLWA   OPCD( 41)
> +#define PLD    OPCD( 57)
> +#define PLXSD  OPCD( 42)
> +#define PLXV   OPCD(25 * 2 + 1)  /* force tx=1 */
> +
> +#define PSTD   OPCD( 61)
> +#define PSTXSD OPCD( 46)
> +#define PSTXV  OPCD(27 * 2 + 1)  /* force sx=1 */
> +
>  #define ADDIC  OPCD( 12)
>  #define ADDI   OPCD( 14)
>  #define ADDIS  OPCD( 15)
> @@ -725,6 +734,20 @@ static ptrdiff_t tcg_pcrel_diff_for_prefix(TCGContext *s, const void *target)
>      return tcg_pcrel_diff(s, target) - (tcg_out_need_prefix_align(s) ? 4 : 0);
>  }
>  
> +/* Output Type 00 Prefix - 8-Byte Load/Store Form (8LS:D) */
> +static void tcg_out_8ls_d(TCGContext *s, tcg_insn_unit opc, unsigned rt,
> +                          unsigned ra, tcg_target_long imm, bool r)
> +{
> +    tcg_insn_unit p, i;
> +
> +    p = OPCD(1) | (r << 20) | ((imm >> 16) & 0x3ffff);
> +    i = opc | TAI(rt, ra, imm);
> +
> +    tcg_out_prefix_align(s);
> +    tcg_out32(s, p);
> +    tcg_out32(s, i);
> +}
> +
>  /* Output Type 10 Prefix - Modified Load/Store Form (MLS:D) */
>  static void tcg_out_mls_d(TCGContext *s, tcg_insn_unit opc, unsigned rt,
>                            unsigned ra, tcg_target_long imm, bool r)
> @@ -1368,6 +1391,49 @@ static void tcg_out_mem_long(TCGContext *s, int opi, int opx, TCGReg rt,
>          break;
>      }
>  
> +    /* For unaligned or large offsets, use the prefixed form. */
> +    if (have_isa_3_10
> +        && (offset != (int16_t)offset || (offset & align))
> +        && offset == sextract64(offset, 0, 34)) {
> +        /*
> +         * Note that the MLS:D insns retain their un-prefixed opcode,
> +         * while the 8LS:D insns use a different opcode space.
> +         */
> +        switch (opi) {
> +        case LBZ:
> +        case LHZ:
> +        case LHA:
> +        case LWZ:
> +        case STB:
> +        case STH:
> +        case STW:
> +        case ADDI:
> +            tcg_out_mls_d(s, opi, rt, base, offset, 0);
> +            return;
> +        case LWA:
> +            tcg_out_8ls_d(s, PLWA, rt, base, offset, 0);
> +            return;
> +        case LD:
> +            tcg_out_8ls_d(s, PLD, rt, base, offset, 0);
> +            return;
> +        case STD:
> +            tcg_out_8ls_d(s, PSTD, rt, base, offset, 0);
> +            return;
> +        case LXSD:
> +            tcg_out_8ls_d(s, PLXSD, rt & 31, base, offset, 0);
> +            return;
> +        case STXSD:
> +            tcg_out_8ls_d(s, PSTXSD, rt & 31, base, offset, 0);
> +            return;
> +        case LXV:
> +            tcg_out_8ls_d(s, PLXV, rt & 31, base, offset, 0);
> +            return;
> +        case STXV:
> +            tcg_out_8ls_d(s, PSTXV, rt & 31, base, offset, 0);
> +            return;
> +        }
> +    }
> +
>      /* For unaligned, or very large offsets, use the indexed form.  */
>      if (offset & align || offset != (int32_t)offset || opi == 0) {
>          if (rs == base) {