On 04/29/2014 04:12 AM, Alex Bennée wrote:
>
> Richard Henderson <r...@twiddle.net> writes:
>
>> And use tcg pointer differencing functions as appropriate.
>>
>> Reviewed-by: Peter Maydell <peter.mayd...@linaro.org>
>> Signed-off-by: Richard Henderson <r...@twiddle.net>
> <snip>
>>
>> -static void tcg_out_branch(TCGContext *s, int call, uintptr_t dest)
>> +static void tcg_out_branch(TCGContext *s, int call, tcg_insn_unit *dest)
>> {
>> - intptr_t disp = dest - (intptr_t)s->code_ptr - 5;
>> + intptr_t disp = tcg_pcrel_diff(s, dest) - 5;
>>
>> if (disp == (int32_t)disp) {
>> tcg_out_opc(s, call ? OPC_CALL_Jz : OPC_JMP_long, 0, 0, 0);
>> tcg_out32(s, disp);
>> } else {
>> - tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_R10, dest);
>> + tcg_out_movi(s, TCG_TYPE_PTR, TCG_REG_R10, (uintptr_t)dest);
>> tcg_out_modrm(s, OPC_GRP5,
>> call ? EXT5_CALLN_Ev : EXT5_JMPN_Ev, TCG_REG_R10);
>> }
>> }
>
> I'm a little unclear on where the -5 came from? Is this a relative
> address based on where we will be after we've emitted the code?
The branch is relative to the end of the branch insn, which itself
is 5 bytes long. I suppose this could be written
dest - (s->code_ptr + 5)
though I don't know if that's any more or less clear.
r~
