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broadcom/compiler: don't assign rf0 to temps that conflict with ldvary

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ldvary writes to rf0 implicitly, so we don't want to allocate rf0 to
any temps that are live across ldvary's rf0 live ranges.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/25450>
This commit is contained in:
Iago Toral Quiroga 2021-10-29 13:00:56 +02:00 • committed by Marge Bot
parent 3a36a618d7
commit cbedf14687
1 changed files with 38 additions and 1 deletions
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39
src/broadcom/compiler/vir_register_allocate.c
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@ -1019,6 +1019,7 @@ static void
update_graph_and_reg_classes_for_inst(struct v3d_compile *c,
int *acc_nodes,
int *implicit_rf_nodes,
int last_ldvary_ip,
struct qinst *inst)
{
int32_t ip = inst->ip;
@ -1125,6 +1126,25 @@ update_graph_and_reg_classes_for_inst(struct v3d_compile *c,
}
}
/* Don't allocate rf0 to temps that cross ranges where we have
* live implicit rf0 writes from ldvary. We can identify these
* by tracking the last ldvary instruction and explicit reads
* of rf0.
*/
if (c->devinfo->ver >= 71 &&
((inst->src[0].file == QFILE_REG && inst->src[0].index == 0) ||
(vir_get_nsrc(inst) > 1 &&
inst->src[1].file == QFILE_REG && inst->src[1].index == 0))) {
for (int i = 0; i < c->num_temps; i++) {
if (c->temp_start[i] < ip &&
c->temp_end[i] > last_ldvary_ip) {
ra_add_node_interference(c->g,
temp_to_node(c, i),
implicit_rf_nodes[0]);
}
}
}
if (inst->dst.file == QFILE_TEMP) {
/* Only a ldunif gets to write to R5, which only has a
* single 32-bit channel of storage.
@ -1270,10 +1290,27 @@ v3d_register_allocate(struct v3d_compile *c)
* interferences.
*/
int ip = 0;
int last_ldvary_ip = -1;
vir_for_each_inst_inorder(inst, c) {
inst->ip = ip++;
/* ldunif(a) always write to a temporary, so we have
* liveness info available to decide if rf0 is
* available for them, however, ldvary is different:
* it always writes to rf0 directly so we don't have
* liveness information for its implicit rf0 write.
*
* That means the allocator may assign rf0 to a temp
* that is defined while an implicit rf0 write from
* ldvary is still live. We fix that by manually
* tracking rf0 live ranges from ldvary instructions.
*/
if (inst->qpu.sig.ldvary)
last_ldvary_ip = ip;
update_graph_and_reg_classes_for_inst(c, acc_nodes,
implicit_rf_nodes, inst);
implicit_rf_nodes,
last_ldvary_ip, inst);
}
/* Set the register classes for all our temporaries in the graph */