Fix off by one errors in linear scan register allocator.
Change-Id: I65eea3cc125e12106a7160d30cb91c5d173bd405
diff --git a/compiler/optimizing/register_allocator.cc b/compiler/optimizing/register_allocator.cc
index 3b51bfb..fc65f97 100644
--- a/compiler/optimizing/register_allocator.cc
+++ b/compiler/optimizing/register_allocator.cc
@@ -260,10 +260,10 @@
// If needed, add interval to the list of unhandled intervals.
if (current->HasSpillSlot() || instruction->IsConstant()) {
- // Split before first register use.
+ // Split just before first register use.
size_t first_register_use = current->FirstRegisterUse();
if (first_register_use != kNoLifetime) {
- LiveInterval* split = Split(current, first_register_use);
+ LiveInterval* split = Split(current, first_register_use - 1);
// Don't add direclty to `unhandled`, it needs to be sorted and the start
// of this new interval might be after intervals already in the list.
AddSorted(&unhandled, split);
@@ -436,6 +436,7 @@
// (1) Remove interval with the lowest start position from unhandled.
LiveInterval* current = unhandled_->Pop();
DCHECK(!current->IsFixed() && !current->HasSpillSlot());
+ DCHECK(unhandled_->IsEmpty() || unhandled_->Peek()->GetStart() >= current->GetStart());
size_t position = current->GetStart();
// (2) Remove currently active intervals that are dead at this position.
@@ -635,7 +636,9 @@
// If the first use of that instruction is after the last use of the found
// register, we split this interval just before its first register use.
AllocateSpillSlotFor(current);
- LiveInterval* split = Split(current, first_register_use);
+ LiveInterval* split = Split(current, first_register_use - 1);
+ DCHECK_NE(current, split) << "There is not enough registers available for "
+ << split->GetParent()->GetDefinedBy()->DebugName();
AddSorted(unhandled_, split);
return false;
} else {
@@ -679,6 +682,7 @@
}
void RegisterAllocator::AddSorted(GrowableArray<LiveInterval*>* array, LiveInterval* interval) {
+ DCHECK(!interval->IsFixed() && !interval->HasSpillSlot());
size_t insert_at = 0;
for (size_t i = array->Size(); i > 0; --i) {
LiveInterval* current = array->Get(i - 1);