To split up the decoder into multiple functions (both to support vendor-specific opcodes in separate files and to simplify maintenance of orthogonal extensions), this changes decode_op to iterate over a table of decoders predicated on guard functions.
This commit only adds the new structure and the table, allowing for the easy addition of additional decoders in the future. Signed-off-by: Philipp Tomsich <philipp.toms...@vrull.eu> --- Changes in v3: - expose only the DisasContext* to predicate functions - mark the table of decoder functions as static - drop the inline from always_true_p, until the need arises (i.e., someone finds a use for it and calls it directly) - rewrite to drop the 'handled' temporary in iterating over the decoder table, removing the assignment in the condition of the if Changes in v2: - (new patch) iterate over a table of guarded decoder functions target/riscv/translate.c | 34 ++++++++++++++++++++++++++++------ 1 file changed, 28 insertions(+), 6 deletions(-) diff --git a/target/riscv/translate.c b/target/riscv/translate.c index 441690846c..38fdec2fd9 100644 --- a/target/riscv/translate.c +++ b/target/riscv/translate.c @@ -111,6 +111,11 @@ static inline bool has_ext(DisasContext *ctx, uint32_t ext) return ctx->misa_ext & ext; } +static bool always_true_p(DisasContext *ctx __attribute__((__unused__))) +{ + return true; +} + #ifdef TARGET_RISCV32 #define get_xl(ctx) MXL_RV32 #elif defined(CONFIG_USER_ONLY) @@ -855,16 +860,26 @@ static uint32_t opcode_at(DisasContextBase *dcbase, target_ulong pc) static void decode_opc(CPURISCVState *env, DisasContext *ctx, uint16_t opcode) { - /* check for compressed insn */ + /* + * A table with predicate (i.e., guard) functions and decoder functions + * that are tested in-order until a decoder matches onto the opcode. + */ + static const struct { + bool (*guard_func)(DisasContext *); + bool (*decode_func)(DisasContext *, uint32_t); + } decoders[] = { + { always_true_p, decode_insn32 }, + }; + + /* Check for compressed insn */ if (extract16(opcode, 0, 2) != 3) { if (!has_ext(ctx, RVC)) { gen_exception_illegal(ctx); } else { ctx->opcode = opcode; ctx->pc_succ_insn = ctx->base.pc_next + 2; - if (!decode_insn16(ctx, opcode)) { - gen_exception_illegal(ctx); - } + if (decode_insn16(ctx, opcode)) + return; } } else { uint32_t opcode32 = opcode; @@ -873,10 +888,17 @@ static void decode_opc(CPURISCVState *env, DisasContext *ctx, uint16_t opcode) ctx->base.pc_next + 2)); ctx->opcode = opcode32; ctx->pc_succ_insn = ctx->base.pc_next + 4; - if (!decode_insn32(ctx, opcode32)) { - gen_exception_illegal(ctx); + + for (size_t i = 0; i < ARRAY_SIZE(decoders); ++i) { + if (!decoders[i].guard_func(ctx)) + continue; + + if (decoders[i].decode_func(ctx, opcode32)) + return; } } + + gen_exception_illegal(ctx); } static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs) -- 2.33.1