On 8/12/20 4:16 PM, Alistair Francis wrote:
> I don't like that we have to manually decode the instructions. As it's
> only a handful it's not the end of the world, but it seems like
> duplication that could grow. Could we not use decode_insn16() instead?
> That way we can share the well tested TCG decoder.
Certainly. Compare how the decoder can be re-purposed for disassembly -- e.g.
target/openrisc/disas.c.
Perhaps something like
typedef uint32_t DisasContext;
#include "decode_insn16.inc.c"
/*
* This function is supposed to be called for an instruction
* that has already executed, and thus is known to be valid.
* That said, return 0 for an invalid instruction.
*/
uint32_t riscv_expand_rvc_to_rvi(uint16_t insn16)
{
uint32_t insn32 = 0; /* illegal instruction */
decode_insn16(&insn32, insn16);
return insn32;
}
static bool expand_i(DisasContext *ctx, arg_immi *a,
uint32_t insn32)
{
insn32 = SET_RD(insn32, a->rd);
insn32 = SET_RS1(insn32, a->rs1);
insn32 = SET_I_IMM(insn32, a->imm);
*ctx = insn32;
return true;
}
static bool trans_addi(DisasContext *ctx, arg_immi *a)
{
return expand_i(ctx, a, OPC_RISC_ADDI);
}
etc. All placed in a new file, so that the myriad symbols don't conflict with
anything else.
r~
