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ra: make the p, q test more efficient

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We can store the q total that pq_test() would've calculated in the node
itself, updating it when we add a node to the stack. This way, we only
have to walk the adjacency list when we push a node on the stack (i.e.
when the p, q test succeeds) instead of every time we do the p, q test.

No difference in shader-db run times, but I'm keeping this in because
the q total that it calculates will also be used in the next few commits.

Signed-off-by: Connor Abbott <connor.abbott@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
This commit is contained in:
Connor Abbott 2014-07-31 18:57:21 -07:00 • committed by Kenneth Graunke
parent 9a0b52e7c1
commit 567e2769b8
1 changed files with 26 additions and 7 deletions
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33
src/mesa/program/register_allocate.c
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@ -146,6 +146,12 @@ struct ra_node {
*/
bool in_stack;
/**
* The q total, as defined in the Runeson/Nyström paper, for all the
* interfering nodes not in the stack.
*/
unsigned int q_total;
/* For an implementation that needs register spilling, this is the
* approximate cost of spilling this node.
*/
@ -354,6 +360,12 @@ ra_add_node_adjacency(struct ra_graph *g, unsigned int n1, unsigned int n2)
{
BITSET_SET(g->nodes[n1].adjacency, n2);
if (n1 != n2) {
int n1_class = g->nodes[n1].class;
int n2_class = g->nodes[n2].class;
g->nodes[n1].q_total += g->regs->classes[n1_class]->q[n2_class];
}
if (g->nodes[n1].adjacency_count >=
g->nodes[n1].adjacency_list_size) {
g->nodes[n1].adjacency_list_size *= 2;
@ -387,6 +399,7 @@ ra_alloc_interference_graph(struct ra_regs *regs, unsigned int count)
g->nodes[i].adjacency_list =
ralloc_array(g, unsigned int, g->nodes[i].adjacency_list_size);
g->nodes[i].adjacency_count = 0;
g->nodes[i].q_total = 0;
ra_add_node_adjacency(g, i, i);
g->nodes[i].reg = NO_REG;
@ -415,20 +428,25 @@ ra_add_node_interference(struct ra_graph *g,
static bool
pq_test(struct ra_graph *g, unsigned int n)
{
unsigned int j;
unsigned int q = 0;
int n_class = g->nodes[n].class;
for (j = 0; j < g->nodes[n].adjacency_count; j++) {
unsigned int n2 = g->nodes[n].adjacency_list[j];
return g->nodes[n].q_total < g->regs->classes[n_class]->p;
}
static void
decrement_q(struct ra_graph *g, unsigned int n)
{
unsigned int i;
int n_class = g->nodes[n].class;
for (i = 0; i < g->nodes[n].adjacency_count; i++) {
unsigned int n2 = g->nodes[n].adjacency_list[i];
unsigned int n2_class = g->nodes[n2].class;
if (n != n2 && !g->nodes[n2].in_stack) {
q += g->regs->classes[n_class]->q[n2_class];
g->nodes[n2].q_total -= g->regs->classes[n2_class]->q[n_class];
}
}
return q < g->regs->classes[n_class]->p;
}
/**
@ -454,6 +472,7 @@ ra_simplify(struct ra_graph *g)
continue;
if (pq_test(g, i)) {
decrement_q(g, i);
g->stack[g->stack_count] = i;
g->stack_count++;
g->nodes[i].in_stack = true;