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Take hreg aliases into account when finding evicted registers and performing

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the register shuffle dance.
This commit is contained in:
David Given 2018-09-22 11:19:50 +02:00
parent bbb708717a
commit 99fcde69dc
1 changed files with 60 additions and 31 deletions
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91
mach/proto/mcg/pass_registerallocator.c
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@ -18,6 +18,8 @@ static int insert_moves(struct basicblock* bb, int index,
static bool type_match(struct hreg* hreg, struct vreg* vreg);
static bool constraints_match(struct hreg* hreg, struct vreg* vreg);
static void populate_hregs(void)
{
int i;
@ -102,33 +104,47 @@ static struct hreg* evict(struct vreg* vreg)
* doing some calculation here to figure out the cheapest register to
* evict, but for now we're picking the first one. FIXME. */
tracef('R', "R: considering evicting a register to rehome %%%d\n", vreg->id);
for (i=0; i<hregs.count; i++)
{
struct hreg* hreg = hregs.item[i];
struct vreg* candidatein = pmap_findleft(current_ins, hreg);
struct vreg* candidateout = pmap_findleft(current_outs, hreg);
if (hreg->attrs & vreg->type)
if ((hreg->attrs & vreg->type) && constraints_match(hreg, vreg))
{
if (!candidatein &&
!candidateout &&
!register_used(current_ins, hreg) &&
!register_used(current_outs, hreg))
{
/* This hreg is unused, so we don't need to evict anything.
* Shouldn't really happen in real life. */
return hreg;
}
if (candidatein && candidateout && (candidatein == candidateout))
{
/* This is a through register. */
tracef('R', "R: evicting %%%d from %s\n", candidatein->id, hreg->id);
pmap_put(&evicted, candidatein, hreg);
pmap_remove(current_ins, hreg, candidatein);
pmap_remove(current_outs, hreg, candidatein);
return hreg;
}
/* Our vreg can be stored in this hreg. But it's only safe to
* evict the hreg if we can also evict all the hreg's aliases. */
int j;
for (j=0; j<hreg->aliases.count; j++)
{
struct hreg* alias = hreg->aliases.item[j];
struct vreg* candidatein = pmap_findleft(current_ins, alias);
struct vreg* candidateout = pmap_findleft(current_outs, alias);
/* Check this is a through. */
if (candidatein != candidateout)
goto next_hreg;
}
/* We've now verified that this hreg is safe to evict. */
for (j=0; j<hreg->aliases.count; j++)
{
struct hreg* alias = hreg->aliases.item[j];
struct vreg* candidatein = pmap_findleft(current_ins, alias);
struct vreg* candidateout = pmap_findleft(current_outs, alias);
/* Check this is a through. */
if (candidatein && (candidatein == candidateout))
{
tracef('R', "R: evicting %%%d from %s so we can use %s\n", candidatein->id, alias->id, hreg->id);
pmap_put(&evicted, candidatein, alias);
pmap_remove(current_ins, alias, candidatein);
pmap_remove(current_outs, alias, candidatein);
}
}
return hreg;
}
next_hreg:;
}
/* Couldn't find anything to evict */
@ -233,7 +249,12 @@ static void add_input_register(struct vreg* vreg, struct hreg* hreg)
if (hreg)
{
if (hreg->is_stacked)
if (!constraints_match(hreg, vreg))
{
/* This hint isn't allowed for this instruction. */
hreg = NULL;
}
else if (hreg->is_stacked)
{
/* This vreg is stacked; we need to put it in a register. That's
* slightly exciting because the vreg might be a through, which
@ -559,7 +580,7 @@ static void assign_hregs_to_vregs(void)
select_registers(hop, old, in, out);
tracef('R', "R: %d from $%d: [", hop->id, hop->ir->id);
tracef('R', "R: %d from $%d: ins: [", hop->id, hop->ir->id);
for (k=0; k<hop->regsin.count; k++)
{
struct hreg* hreg = hop->regsin.item[k].left;
@ -568,7 +589,7 @@ static void assign_hregs_to_vregs(void)
tracef('R', " ");
tracef('R', "%%%d=>%s", vreg->id, hreg->id);
}
tracef('R', "] [");
tracef('R', "] outs: [");
for (k=0; k<hop->regsout.count; k++)
{
struct hreg* hreg = hop->regsout.item[k].left;
@ -612,17 +633,25 @@ static int insert_moves(struct basicblock* bb, int index,
struct hreg* other;
struct hop* hop;
/* Try and find a destination which isn't a source. */
/* Try and find a destination which isn't a source (or an alias of a source). */
src = NULL;
for (i=0; i<copies.count; i++)
{
int j;
dest = copies.item[i].right;
if (!pmap_findleft(&copies, dest))
{
src = copies.item[i].left;
break;
}
for (j=0; j<dest->aliases.count; j++)
{
struct hreg* alias = dest->aliases.item[j];
if (pmap_findleft(&copies, alias))
goto nextcopy;
}
src = copies.item[i].left;
break;
nextcopy:;
}
if (src)