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target/riscv: iterate over a table of decoders 

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.tomsich@vrull.eu>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220202005249.3566542-6-philipp.tomsich@vrull.eu>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
This commit is contained in:
Philipp Tomsich 2022-02-02 01:52:47 +01:00 committed by Alistair Francis
parent f2a32bec8f
commit 5e199b6bdc
1 changed files with 27 additions and 5 deletions
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32
target/riscv/translate.c
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@ -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)
@ -855,15 +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 {
@ -873,10 +889,16 @@ 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) &&
decoders[i].decode_func(ctx, opcode32)) {
return;
}
}
}
gen_exception_illegal(ctx);
}
static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)