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#include "lisc.h"
/* For x86_64, we have to:
*
* - check that constants are used only in
* places allowed by the machine
*
* - explicit machine register contraints
* on instructions like division.
*
* - lower calls (future, I have to think
* about their representation and the
* way I deal with structs/unions in the
* ABI)
*/
extern Ins insb[NIns], *curi; /* shared work buffer */
static void
emit(short op, Ref to, Ref arg0, Ref arg1)
{
if (curi == insb)
diag("isel: too many instructions");
*--curi = (Ins){op, to, {arg0, arg1}};
}
static int
newtmp(int type, Fn *fn)
{
static int n;
int t;
t = fn->ntmp++;
fn->tmp = realloc(fn->tmp, fn->ntmp * sizeof fn->tmp[0]);
if (!fn->tmp)
diag("isel: out of memory");
fn->tmp[t] = (Tmp){.type = type};
sprintf(fn->tmp[t].name, "isel%d", ++n);
return t;
}
static int
cneg(int cmp)
{
switch (cmp) {
default: diag("cneg: unhandled comparison");
case Ceq: return Cne;
case Csle: return Csgt;
case Cslt: return Csge;
case Csgt: return Csle;
case Csge: return Cslt;
case Cne: return Ceq;
}
}
static int
islong(Ref r, Fn *fn)
{
return rtype(r) == RTmp && fn->tmp[r.val].type == TLong;
}
static void
selcmp(Ref arg[2], Fn *fn)
{
Ref r;
int t;
t = -1;
if (rtype(arg[0]) == RCon) {
r = arg[1];
arg[1] = arg[0];
arg[0] = r;
if (rtype(r) == RCon) {
/* todo, use the constant
* size to dimension the
* constant */
t = newtmp(TWord, fn);
arg[0] = TMP(t);
}
}
if (islong(arg[0], fn) || islong(arg[1], fn))
emit(OXCmpl, R, arg[1], arg[0]);
else
emit(OXCmpw, R, arg[1], arg[0]);
if (t != -1)
emit(OCopy, TMP(t), r, R);
}
static void
sel(Ins i, Fn *fn)
{
Ref r0, r1, ra, rd;
int t, ty, c;
switch (i.op) {
case ODiv:
case ORem:
ty = fn->tmp[i.to.val].type;
switch (ty) {
default:
diag("isel: invalid division");
case TWord:
ra = REG(EAX);
rd = REG(EDX);
break;
case TLong:
ra = REG(RAX);
rd = REG(RDX);
break;
}
r0 = i.op == ODiv ? ra : rd;
r1 = i.op == ODiv ? rd : ra;
emit(OCopy, i.to, r0, R);
emit(OCopy, R, r1, R);
if (rtype(i.arg[1]) == RCon) {
/* immediates not allowed for
* divisions in x86
*/
t = newtmp(ty, fn);
r0 = TMP(t);
} else
r0 = i.arg[1];
emit(OXDiv, R, r0, R);
emit(OSign, rd, ra, R);
emit(OCopy, ra, i.arg[0], R);
if (rtype(i.arg[1]) == RCon)
emit(OCopy, r0, i.arg[1], R);
break;
case OAdd:
case OSub:
case OCopy:
emit(i.op, i.to, i.arg[0], i.arg[1]);
break;
default:
if (OCmp <= i.op && i.op <= OCmp1) {
c = i.op - OCmp;
if (rtype(i.arg[0]) == RCon)
c = COP(c);
emit(OXSet+c, i.to, R, R);
selcmp(i.arg, fn);
break;
}
diag("isel: non-exhaustive implementation");
}
}
static Ins *
flagi(Ins *i0, Ins *i)
{
while (i>i0)
switch ((--i)->op) {
default:
return i;
case OCopy:
case OStore:
case OLoad:;
}
return 0;
}
static Ins *
seljmp(Blk *b, Fn *fn)
{
Ref r;
int c;
Ins *fi;
fi = &b->ins[b->nins];
if (b->jmp.type != JJez)
return fi;
r = b->jmp.arg;
b->jmp.arg = R;
assert(!req(r, R));
if (rtype(r) == RCon) {
b->jmp.type = JJmp;
if (!req(r, CON_Z))
b->s1 = b->s2;
b->s2 = 0;
return fi;
}
fi = flagi(b->ins, fi);
if (fi && req(fi->to, r)) {
assert(1 == fn->tmp[r.val].nuse);
if (fn->tmp[r.val].nuse == 1
&& OCmp <= fi->op && fi->op <= OCmp1) {
c = fi->op - OCmp;
if (rtype(fi->arg[0]) == RCon)
c = COP(c);
b->jmp.type = JXJc + cneg(c);
selcmp(fi->arg, fn);
return fi;
}
/* what if it is a comparison
* that is used more than once?
* !!!
*/
b->jmp.type = JXJc + Ceq;
return fi+1;
}
if (islong(r, fn))
emit(OXCmpl, R, CON_Z, r);
else
emit(OXCmpw, R, CON_Z, r);
b->jmp.type = JXJc + Ceq;
return &b->ins[b->nins];
}
/* instruction selection
* requires use counts (as given by parsing)
*/
void
isel(Fn *fn)
{
Blk *b;
Ins *i;
uint nins;
for (b=fn->start; b; b=b->link) {
curi = &insb[NIns];
i = seljmp(b, fn);
while (i>b->ins) {
sel(*--i, fn);
}
nins = &insb[NIns] - curi;
free(b->ins);
b->ins = alloc(nins * sizeof b->ins[0]);
memcpy(b->ins, curi, nins * sizeof b->ins[0]);
b->nins = nins;
}
}
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