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cheaper mul by small constants on amd64

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This commit is contained in:
Quentin Carbonneaux 2024-06-18 17:00:30 +02:00
parent 96f18be71d
commit 6dab93b4b2
1 changed files with 56 additions and 0 deletions
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56
amd64/emit.c
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@ -360,6 +360,54 @@ Next:
goto Next;
}
static int
mulops(int depth, int *ops, int64_t k)
{
static int tab[] = {9, 8, 5, 4, 3, 2, 1, 0};
int *pm, m;
while (depth && k>1) {
for (pm=tab; (m=*pm); pm++)
if (k % m == 0) {
*ops++ = m;
depth -= 1;
k /= m;
goto next;
}
return 0;
next:;
}
*ops = 1;
return k == 1;
}
static int
emitmulk(Ref to, Ref r, int64_t k, Ins *i, Fn *fn, FILE *f)
{
int ops[3], *pm, m;
char fmt[32];
if (k == 1 || !mulops(2, ops, k))
return 0;
for (pm=ops; (m=*pm) != 1; pm++) {
if (m == 4 || m == 2) {
if (!req(r, to))
emitf("mov%k %1, %=", i, fn, f);
emitf("add%k %=, %=", i, fn, f);
if (m == 4)
emitf("add%k %=, %=", i, fn, f);
} else {
sprintf(fmt, "lea%%k (%s, %%1, %d), %%=",
(m & 1) ? "%1" : "", m & ~1);
emitf(fmt, i, fn, f);
}
r = to;
i->arg[1] = to;
}
return 1;
}
static void *negmask[4] = {
[Ks] = (uint32_t[4]){ 0x80000000 },
[Kd] = (uint64_t[2]){ 0x8000000000000000 },
@ -407,6 +455,14 @@ emitins(Ins i, Fn *fn, FILE *f)
i.arg[0] = i.arg[1];
i.arg[1] = r;
}
if (KBASE(i.cls) == 0)
if (rtype(i.arg[0]) == RCon) {
con = &fn->con[i.arg[0].val];
val = con->bits.i;
if (con->type == CBits)
if (emitmulk(i.to, i.arg[1], val, &i, fn, f))
break;
}
if (KBASE(i.cls) == 0 /* only available for ints */
&& rtype(i.arg[0]) == RCon
&& rtype(i.arg[1]) == RTmp) {