On Fri, Mar 07, 2008 at 06:07:32PM +0200, Blue Swirl wrote:
> On 3/7/08, Stuart Brady <[EMAIL PROTECTED]> wrote:
> > I do understand that the current SPARC TCG code is preliminary work.
> > However, in some ways, I feel it still serves as a better reference than
> > i386 and x86_64
>
> Well, I'd still recommend using x86 as a reference until Sparc works
> or you may copy a faulty design.
Don't worry -- I still checked with the x86 targets. I only really
needed a quick idea of what was required for a new target.
> > Which registers should go in tcg_target_reg_alloc_order[]? I notice
> > that i386 includes ESP, which tcg_target_init() marks as reserved, and
> > x86_64 includes RBX and RBP, which are again marked as reserved.
>
> I put there only the registers that should be safe to use, the G
> registers may have issues or they are already used as global
> registers. Also we should not need frame pointer.
Sounds reasonable. I think I really meant to ask what _shouldn't_ go in
tcg_target_reg_alloc_order[]. I was mainly confused by the inclusion of
registers which are marked as reserved on the x86 targets.
> > Furthermore, x86_64's tcg_target_reg_alloc_order[] contains 16 elements
> > (TCG_TARGET_NB_REGS), but only 15 are specified -- the last element is
> > left as 0, which is TCG_REG_RAX. SPARC also does this, but with
> > TARGET_REG_G0 (which is marked as reserved, as it's hardwired to zero).
>
> Maybe I missed something, but g0 isn't in the reg_alloc_order?
tcg_target_reg_alloc_order[] has 32 elements, but only 14 are used.
The rest hold 0, specifying TCG_REG_G0.
> > On SPARC, I notice that goto_tb is handled using CALL and JMPL, placing
> > the return address in o7... but we're returning from a TB, or jumping to
> > another one, so surely we shouldn't link here? Also, TCG_TYPE_TL is
> > used for exit_tb's return value, I think this should be the host's long
> > (using TCG_TYPE_PTR) instead.
>
> These are bugs, thanks for spotting. I was using o7 if a register is
> needed, it will be clobbered anyway.
I don't understand -- o7 is required when returning in exit_tb, so if it
is used, it must be saved and restored.
> > Also on SPARC, could the indentation of the OP_32_64s be improved?
> > Yeah, it's not a serious problem, but I feel it would make the code
> > slightly easier to read.
>
> It's not my fault, Emacs wants to do it this way. I'm open to your
> suggestions.
Oh dear, I'm such a vim user, I don't even have Emacs installed. :)
How about something like this?
#if defined(__sparc_v9__) && !defined(__sparc_v8plus__)
#define OP_32_64(x) \
glue(glue(case INDEX_op_, x), _i32:) \
glue(glue(case INDEX_op_, x), _i64)
#else
#define OP_32_64(x) \
glue(glue(case INDEX_op_, x), _i32)
#endif
...
OP_32_64(ld8u):
tcg_out_ldst(s, args[0], args[1], args[2], LDUB);
break;
...
The macro might be a bit sick, but hopefully it would make Emacs happy,
and I feel ':' does make a certain amount of sense, here.
It probably wouldn't help with indentation, but you could always do
something like this:
#if defined(__sparc_v9__) && !defined(__sparc_v8plus__)
#define v9(x) x
#else
#define v9(x)
#endif
...
case INDEX_op_ld8u_i32:
v9( case INDEX_op_ld8u_i64: )
tcg_out_ldst(s, args[0], args[1], args[2], LDUB);
break;
...
I'll admit, that looks unusual, but it would avoid breaking searches for
ld8u_i32 or op_ld8u.
Cheers,
--
Stuart Brady
