ref: e6634fbd0c3e091d6db26c4290d6b31e1e7a36e7
parent: 380adf8b485ce93aa42ad0d414718c3ad4918176
author: cinap_lenrek <[email protected]>
date: Sat Apr 18 21:25:35 EDT 2020
6c: conserve registers for floating point operations
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.
--- a/sys/src/cmd/6c/cgen.c
+++ b/sys/src/cmd/6c/cgen.c
@@ -824,9 +824,9 @@
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);