Bill Coffman <[EMAIL PROTECTED]> wrote:
> On Wed, 17 Nov 2004 14:14:18 +0100, Leopold Toetsch <[EMAIL PROTECTED]> wrote:
>> I've now (locally here) extended Bill Coffman's register allocator by
>> one subroutine that actually decides to use non-volatiles or volatiles
>> according to pdd03. All variables that are live around a subroutine call
>> are e.g. allocated from R16..R31.
> Interesting. I'd like to see it.
See below, you know where it's called from ;)
> Regarding pdd03, I am still not clear how it should be interpreted.
All registers are preserved, but some of these registers are used,
either by implict opcodes or as return values.
> * If the subroutine being allocated is a leaf (with no sub calls),
> then all registers should be available.
Yep.
> * Registers P4, S1-S4, N0-N4 are free for allocation, regardless.
I've included P3 (see below). If it's used it interfers.
> * It seems like it would be simple enough to provide a "compiler
> hint", to let the allocator know if the subs it calls are using the
> parrot convention or not, or how many of the R5-R15 it will need.
The register allocator is only supporting pdd03, nothing else. The
amount of needed R5 - R15 is unknown, as these are return results.
> ... This can then be used as part of a static analysis,
> and can be incorporated into the unit data structure, or passed as a
> separate parameter to imc_reg_alloc().
Yep and it's working.
> ~Bill
leo
/*
* find available color for register #x in available colors
*/
static int
ig_find_color(Interp* interpreter, IMC_Unit *unit, int x, char *avail)
{
int c, t;
SymReg *r;
static const char types[] = "ISPN";
static const char assignable[4][5] = {
/* 0 1 2 3 4 */
{ 0, 0, 0, 0, 0, }, /* I */
{ 0, 1, 1, 1, 1, }, /* S */
{ 0, 0, 0, 1, 1, }, /* P */
{ 1, 1, 1, 1, 1, }, /* N */
};
UNUSED(interpreter);
r = unit->reglist[x];
t = strchr(types, r->set) - types;
/* please note: c is starting at 1 for R0 */
if (!(r->usage & U_NON_VOLATILE)) {
/* 0) 5-15 volatile range */
for (c = 6; c <= 16; c++)
if (avail[c])
return c;
}
/* 1) try upper non-volatiles, 16...31 */
for (c = 17; c <= 32; c++)
if (avail[c])
return c;
/* some lower regs are preserved too 0...4 */
for (c = 1; c <= 5; c++)
if (avail[c] && assignable[t][c - 1])
return c;
/* no chance, force high range with possible spilling */
for (c = 33; ; c++)
if (avail[c])
return c;
assert(0);
return 0;
}
