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// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/compiler/live-range-separator.h"
#include "src/compiler/register-allocator.h"
namespace v8 {
namespace internal {
namespace compiler {
#define TRACE(...) \
do { \
if (FLAG_trace_alloc) PrintF(__VA_ARGS__); \
} while (false)
namespace {
void CreateSplinter(TopLevelLiveRange *range, RegisterAllocationData *data,
LifetimePosition first_cut, LifetimePosition last_cut) {
DCHECK(!range->IsSplinter());
// We can ignore ranges that live solely in deferred blocks.
// If a range ends right at the end of a deferred block, it is marked by
// the range builder as ending at gap start of the next block - since the
// end is a position where the variable isn't live. We need to take that
// into consideration.
LifetimePosition max_allowed_end = last_cut.NextFullStart();
if (first_cut <= range->Start() && max_allowed_end >= range->End()) {
return;
}
LifetimePosition start = Max(first_cut, range->Start());
LifetimePosition end = Min(last_cut, range->End());
if (start < end) {
// Ensure the original range has a spill range associated, before it gets
// splintered. Splinters will point to it. This way, when attempting to
// reuse spill slots of splinters, during allocation, we avoid clobbering
// such slots.
if (range->MayRequireSpillRange()) {
data->CreateSpillRangeForLiveRange(range);
}
if (range->splinter() == nullptr) {
TopLevelLiveRange *splinter = data->NextLiveRange(range->machine_type());
DCHECK_NULL(data->live_ranges()[splinter->vreg()]);
data->live_ranges()[splinter->vreg()] = splinter;
range->SetSplinter(splinter);
}
Zone *zone = data->allocation_zone();
TRACE("creating splinter for range %d between %d and %d\n", range->vreg(),
start.ToInstructionIndex(), end.ToInstructionIndex());
range->Splinter(start, end, zone);
}
}
int FirstInstruction(const UseInterval *interval) {
LifetimePosition start = interval->start();
int ret = start.ToInstructionIndex();
if (start.IsInstructionPosition() && start.IsEnd()) {
++ret;
}
return ret;
}
int LastInstruction(const UseInterval *interval) {
LifetimePosition end = interval->end();
int ret = end.ToInstructionIndex();
if (end.IsGapPosition() || end.IsStart()) {
--ret;
}
return ret;
}
void SplinterLiveRange(TopLevelLiveRange *range, RegisterAllocationData *data) {
const InstructionSequence *code = data->code();
UseInterval *interval = range->first_interval();
LifetimePosition first_cut = LifetimePosition::Invalid();
LifetimePosition last_cut = LifetimePosition::Invalid();
while (interval != nullptr) {
UseInterval *next_interval = interval->next();
const InstructionBlock *first_block =
code->GetInstructionBlock(FirstInstruction(interval));
const InstructionBlock *last_block =
code->GetInstructionBlock(LastInstruction(interval));
int first_block_nr = first_block->rpo_number().ToInt();
int last_block_nr = last_block->rpo_number().ToInt();
for (int block_id = first_block_nr; block_id <= last_block_nr; ++block_id) {
const InstructionBlock *current_block =
code->InstructionBlockAt(RpoNumber::FromInt(block_id));
if (current_block->IsDeferred()) {
if (!first_cut.IsValid()) {
first_cut = LifetimePosition::GapFromInstructionIndex(
current_block->first_instruction_index());
}
last_cut = LifetimePosition::GapFromInstructionIndex(
current_block->last_instruction_index());
} else {
if (first_cut.IsValid()) {
CreateSplinter(range, data, first_cut, last_cut);
first_cut = LifetimePosition::Invalid();
last_cut = LifetimePosition::Invalid();
}
}
}
interval = next_interval;
}
// When the range ends in deferred blocks, first_cut will be valid here.
// Splinter from there to the last instruction that was in a deferred block.
if (first_cut.IsValid()) {
CreateSplinter(range, data, first_cut, last_cut);
}
}
} // namespace
void LiveRangeSeparator::Splinter() {
size_t virt_reg_count = data()->live_ranges().size();
for (size_t vreg = 0; vreg < virt_reg_count; ++vreg) {
TopLevelLiveRange *range = data()->live_ranges()[vreg];
if (range == nullptr || range->IsEmpty() || range->IsSplinter()) {
continue;
}
SplinterLiveRange(range, data());
}
}
void LiveRangeMerger::Merge() {
int live_range_count = static_cast<int>(data()->live_ranges().size());
for (int i = 0; i < live_range_count; ++i) {
TopLevelLiveRange *range = data()->live_ranges()[i];
if (range == nullptr || range->IsEmpty() || !range->IsSplinter()) {
continue;
}
TopLevelLiveRange *splinter_parent = range->splintered_from();
int to_remove = range->vreg();
splinter_parent->Merge(range, data()->allocation_zone());
data()->live_ranges()[to_remove] = nullptr;
}
}
} // namespace compiler
} // namespace internal
} // namespace v8
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