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6c: conserve registers for floating point operations

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for floating point operations, reuse the return register
on the right hand side if it has higher complex number
than the left hand side to conserve registers.

this makes the following code compile, that was previously
run out of floating point register:

float
f(float r[15])
{
	return (r[0] + (r[1] * (r[2] + r[3] * (r[4] + r[5] * (r[6] + r[7] * (r[8] + r[9] * (r[10] + r[11] * (r[12] + r[13] * r[14]))))))));
}

the downside is that this produces extra move operations.
This commit is contained in:
cinap_lenrek 2020-04-19 01:25:35 +02:00
parent 380adf8b48
commit e6634fbd0c
1 changed files with 2 additions and 2 deletions
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4
sys/src/cmd/6c/cgen.c
View file

@ -824,9 +824,9 @@ cgen(Node *n, Node *nn)
gopcode(o, n->type, r, &nod);
} else {
/* TO DO: could do better with r->addable >= INDEXED */
regalloc(&nod1, r, Z);
regalloc(&nod1, r, nn);
cgen(r, &nod1);
regalloc(&nod, l, nn);
regalloc(&nod, l, Z);
cgen(l, &nod);
gopcode(o, n->type, &nod1, &nod);
regfree(&nod1);