On 4/14/21 12:11 PM, Richard Henderson wrote:
This approach seems like it will work fine for MLS and MMIR prefixes. For 8LS,
8RR, and MRR prefixes, we'll need some extra help within ppc_tr_translate_insn.
E.g.
insn = translator_ldl_swap(env, ctx->base.pc_next,
need_byteswap(ctx));
switch (ctx->prefix_type) {
case PREFIX_NONE:
ok = decode_opcode_space_0(ctx, insn) ||
decode_legacy(ctx, insn);
break;
case PREFIX_MLS:
case PREFIX_MMIRR:
ok = decode_opcode_space_0(ctx, insn);
break;
I played about with this last night, and there's an interesting trade-off:
(1) The thousands of 32-bit insns which do not allow prefixes
now each require 3 lines to assert that no prefix is present,
(2) There are only 12 MLS and 29 MMIRR prefixed insns.
I think it may well be that eliminating boiler-plate from thousands of insns it
a good trade-off to special-casing 41 insns.
At which point, considering the multiple variations on 8RR and MMIRR prefixes,
seems to indicate that we should decode all 64 bits all at once.
r~
