static bool
qir_opt_peephole_sf_block(struct vc4_compile *c, struct qblock *block)
{
bool progress = false;
/* We don't have liveness dataflow analysis for flags, but we also
* never generate a use of flags across control flow, so just treat
* them as unused at block exit.
*/
bool sf_live = false;
struct qinst *last_sf = NULL;
/* Walk the block from bottom to top, tracking if the SF is used, and
* removing unused or repeated ones.
*/
qir_for_each_inst_rev(inst, block) {
if (inst->sf) {
if (!sf_live) {
/* Our instruction's SF isn't read, so drop it.
*/
dump_from(c, inst, "dead SF");
inst->sf = false;
dump_to(c, inst);
progress = true;
} else if (last_sf &&
inst_result_equals(last_sf, inst)) {
/* The last_sf sets up same value as inst, so
* just drop the later one.
*/
dump_from(c, last_sf, "repeated SF");
last_sf->sf = false;
dump_to(c, last_sf);
progress = true;
last_sf = inst;
} else {
last_sf = inst;
}
sf_live = false;
}
if (last_sf) {
if (inst_srcs_updated(last_sf, inst))
last_sf = NULL;
}
if (qir_depends_on_flags(inst))
sf_live = true;
}
return progress;
}
bool
qir_opt_peephole_sf(struct vc4_compile *c)
{
bool progress = false;
bool sf_live = false;
struct qinst *last_sf = NULL;
/* Walk the block from bottom to top, tracking if the SF is used, and
* removing unused or repeated ones.
*/
list_for_each_entry_rev(struct qinst, inst, &c->instructions, link) {
if (inst->sf) {
if (!sf_live) {
/* Our instruction's SF isn't read, so drop it.
*/
dump_from(c, inst, "dead SF");
inst->sf = false;
dump_to(c, inst);
progress = true;
} else if (last_sf &&
inst_result_equals(last_sf, inst)) {
/* The last_sf sets up same value as inst, so
* just drop the later one.
*/
dump_from(c, last_sf, "repeated SF");
last_sf->sf = false;
dump_to(c, last_sf);
progress = true;
last_sf = inst;
} else {
last_sf = inst;
}
sf_live = false;
}
if (last_sf) {
if (inst_srcs_updated(last_sf, inst))
last_sf = NULL;
}
if (qir_depends_on_flags(inst))
sf_live = true;
}
return progress;
}
