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Track register pressure for dead EBB parameters.

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The spiller wasn't tracking register pressure correctly for dead EBB
parameters in visit_ebb_header(). Make sure we free any dead EBB
parameters.

Fixes #223
This commit is contained in:
Jakob Stoklund Olesen
2018-01-17 12:39:10 -08:00
parent 5463fde203
commit 13af22b46b
5 changed files with 204 additions and 17 deletions
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33
lib/cretonne/src/regalloc/spilling.rs
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@@ -120,7 +120,8 @@ impl<'a> Context<'a> {
dbg!("Spilling {}:", ebb);
self.cur.goto_top(ebb);
self.visit_ebb_header(ebb, tracker);
tracker.drop_dead_args();
tracker.drop_dead_params();
self.process_spills(tracker);
while let Some(inst) = self.cur.next_inst() {
if let Some(constraints) =
@@ -163,8 +164,22 @@ impl<'a> Context<'a> {
}
}
// Free all dead registers in `regs` from the pressure set.
fn free_dead_regs(&mut self, regs: &[LiveValue]) {
for lv in regs {
if lv.is_dead {
if let Affinity::Reg(rci) = lv.affinity {
if !self.spills.contains(&lv.value) {
let rc = self.reginfo.rc(rci);
self.pressure.free(rc);
}
}
}
}
}
fn visit_ebb_header(&mut self, ebb: Ebb, tracker: &mut LiveValueTracker) {
let (liveins, args) = tracker.ebb_top(
let (liveins, params) = tracker.ebb_top(
ebb,
&self.cur.func.dfg,
self.liveness,
@@ -177,22 +192,17 @@ impl<'a> Context<'a> {
self.pressure.reset();
self.take_live_regs(liveins);
// An EBB can have an arbitrary (up to 2^16...) number of EBB arguments, so they are not
// An EBB can have an arbitrary (up to 2^16...) number of parameters, so they are not
// guaranteed to fit in registers.
for lv in args {
for lv in params {
if let Affinity::Reg(rci) = lv.affinity {
let rc = self.reginfo.rc(rci);
'try_take: while let Err(mask) = self.pressure.take_transient(rc) {
dbg!(
"Need {} reg for EBB argument {} from {} live-ins",
rc,
lv.value,
liveins.len()
);
dbg!("Need {} reg for EBB param {}", rc, lv.value);
match self.spill_candidate(mask, liveins) {
Some(cand) => {
dbg!(
"Spilling live-in {} to make room for {} EBB argument {}",
"Spilling live-in {} to make room for {} EBB param {}",
cand,
rc,
lv.value
@@ -217,6 +227,7 @@ impl<'a> Context<'a> {
// The transient pressure counts for the EBB arguments are accurate. Just preserve them.
self.pressure.preserve_transient();
self.free_dead_regs(params);
}
fn visit_inst(