Re: [PATCH 13/28] tcg/mips: Support bswap flags in tcg_out_bswap16

[Richard Henderson <richard.henderson@linaro.org>]

On 6/21/21 11:36 PM, Philippe Mathieu-Daudé wrote:
>                                                          /* src = abcd
> efgh */
>      if (use_mips32r2_instructions) {
>          tcg_out_opc_reg(s, OPC_WSBH, ret, 0, arg);      /* ret = cdab
> ghef */

badc -- bytes swapped in halfwords.  Also, this is a 32-bit insn, so 4 bytes is sufficient.

>          if (flags & TCG_BSWAP_OS) {
>              tcg_out_opc_reg(s, OPC_SEH, ret, 0, ret);   /* ret = ssss
> ghef */

(ssss)ssdc

Again, 32-bit insn, but implicitly sign-extending to 64-bits as per standard mips convention.

>          } else if ((flags & (TCG_BSWAP_IZ | TCG_BSWAP_OZ)) ==
> TCG_BSWAP_OZ) {
>              tcg_out_opc_imm(s, OPC_ANDI, ret, ret, 0xffff);
>                                                          /* ret = 0000
> ghef */

(0000)00dc.

>      tcg_out_opc_sa(s, OPC_SRL, TCG_TMP0, arg, 8);       /* t0  = ssab
> cdef */
>      if (!(flags & TCG_BSWAP_IZ)) {                      /* t0  = 0000
> 00ef */
>          tcg_out_opc_imm(s, OPC_ANDI, TCG_TMP0, TCG_TMP0, 0x00ff);
>      }
>      if (flags & TCG_BSWAP_OS) {
>          tcg_out_opc_sa(s, OPC_SLL, ret, arg, 24);       /* ret = gh..
> .... */
>          tcg_out_opc_sa(s, OPC_SRA, ret, ret, 16);       /* ret = ssss
> gh.. */
>      } else {
>          tcg_out_opc_sa(s, OPC_SLL, ret, arg, 8);        /* ret = cdef
> gh.. */
>          if (flags & TCG_BSWAP_OZ) {                     /* ret = 0000
> gh.. */
>              tcg_out_opc_imm(s, OPC_ANDI, ret, ret, 0xff00);
>          }
>      }
>      tcg_out_opc_reg(s, OPC_OR, ret, ret, TCG_TMP0); /* OZ: ret = 0000
> ghef */
>                                                      /* OS: ret = ssss
> ghef */

Something like that, yes.  I'll fix it up.


r~