[turbofan] Stand-alone deferred block splitting - full.

src/compiler/preprocess-live-ranges.cc

 // 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/preprocess-live-ranges.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 {
+
+LiveRange* Split(LiveRange* range, RegisterAllocationData* data,
+                 LifetimePosition pos) {
+  DCHECK(range->Start() < pos && pos < range->End());
+  DCHECK(pos.IsStart() || pos.IsGapPosition() ||
+         (data->code()
+              ->GetInstructionBlock(pos.ToInstructionIndex())
+              ->last_instruction_index() != pos.ToInstructionIndex()));
+  LiveRange* result = data->NewChildRangeFor(range);
+  range->SplitAt(pos, result, data->allocation_zone());
+  TRACE("Split range %d(v%d) @%d => %d.\n", range->id(),
+        range->TopLevel()->id(), pos.ToInstructionIndex(), result->id());
+  return result;
+}
+
+
+LifetimePosition GetSplitPositionForInstruction(const LiveRange* range,
+                                                int instruction_index) {
+  LifetimePosition ret = LifetimePosition::Invalid();
+
+  ret = LifetimePosition::GapFromInstructionIndex(instruction_index);
+  if (range->Start() >= ret || ret >= range->End()) {
+    return LifetimePosition::Invalid();
+  }
+  return ret;
+}
+
+
+LiveRange* SplitRangeAfterBlock(LiveRange* range, RegisterAllocationData* data,
+                                const InstructionBlock* block) {
+  const InstructionSequence* code = data->code();
+  int last_index = block->last_instruction_index();
+  int outside_index = static_cast<int>(code->instructions().size());
+  bool has_handler = false;
+  for (auto successor_id : block->successors()) {
+    const InstructionBlock* successor = code->InstructionBlockAt(successor_id);
+    if (successor->IsHandler()) {
+      has_handler = true;
+    }
+    outside_index = Min(outside_index, successor->first_instruction_index());
+  }
+  int split_at = has_handler ? outside_index : last_index;
+  LifetimePosition after_block =
+      GetSplitPositionForInstruction(range, split_at);
+
+  if (after_block.IsValid()) {
+    return Split(range, data, after_block);
+  }
+
+  return range;
+}
+
+
+int GetFirstInstructionIndex(const UseInterval* interval) {
+  int ret = interval->start().ToInstructionIndex();
+  if (!interval->start().IsGapPosition() && !interval->start().IsStart()) {
+    ++ret;
+  }
+  return ret;
+}
+
+
+bool DoesSubsequenceClobber(const InstructionSequence* code, int start,
+                            int stop) {

[Jarin, 2015/08/04 19:39:43]

stop -> end

[Mircea Trofin, 2015/08/04 20:34:46]

Done.

+  for (int i = start; i <= stop; ++i) {
+    if (code->InstructionAt(i)->IsCall()) return true;
+  }
+  return false;
+}
+
+
+void SplitRangeByClobberingDeferredBlocks(LiveRange* range,

[Jarin, 2015/08/04 19:39:43]

The name is a bit confusing (it sounds like it clobbers deferred blocks).
Perhaps SplitRangeAtDeferredBlocksWithCalls?

[Mircea Trofin, 2015/08/04 20:34:46]

Done.

+                                          RegisterAllocationData* data) {
+  DCHECK(!range->IsFixed());
+  DCHECK(!range->spilled());
+  if (range->TopLevel()->HasSpillOperand()) {
+    TRACE(
+        "Skipping deferred block analysis for live range %d because it has a "
+        "spill operand.\n",
+        range->TopLevel()->id());
+    return;
+  }
+
+  const InstructionSequence* code = data->code();
+  LiveRange* current_subrange = range;
+
+  UseInterval* interval = current_subrange->first_interval();
+
+  while (interval != nullptr) {
+    int first_index = GetFirstInstructionIndex(interval);
+    int last_index = interval->end().ToInstructionIndex();
+
+    if (last_index >= code->InstructionCount()) {

[Jarin, 2015/08/04 19:39:43]

It could be more readable if you said "if (last_index >
code->LastInstructionIndex()) last_index = code->LastInstructionIndex();". With
that, you could remove the InstructionCount method.

[Mircea Trofin, 2015/08/04 20:34:46]

Done.

+      last_index = code->LastInstructionIndex();
+    }
+    interval = interval->next();
+
+    for (int index = first_index; index <= last_index;) {
+      const InstructionBlock* block = code->GetInstructionBlock(index);
+      int last_block_index = static_cast<int>(block->last_instruction_index());
+      int last_covered_index = Min(last_index, last_block_index);
+      int working_index = index;
+      index = block->last_instruction_index() + 1;
+
+      if (!block->IsDeferred() ||
+          !DoesSubsequenceClobber(code, working_index, last_covered_index)) {
+        continue;
+      }
+
+      TRACE("Deferred block B%d clobbers range %d(v%d).\n",
+            block->rpo_number().ToInt(), current_subrange->id(),
+            current_subrange->TopLevel()->id());
+      LifetimePosition block_start =
+          GetSplitPositionForInstruction(current_subrange, working_index);
+      LiveRange* block_and_after = nullptr;
+      if (block_start.IsValid()) {
+        block_and_after = Split(current_subrange, data, block_start);
+      } else {
+        block_and_after = current_subrange;
+      }
+      LiveRange* next = SplitRangeAfterBlock(block_and_after, data, block);
+      if (next != current_subrange) interval = next->first_interval();
+      current_subrange = next;
+      break;
+    }
+  }
+}
+}
+
+
 void PreprocessLiveRanges::PreprocessRanges() {
   SplitRangesAroundDeferredBlocks();
 }
 
 
-void PreprocessLiveRanges::SplitRangesAroundDeferredBlocks() {}
-
+void PreprocessLiveRanges::SplitRangesAroundDeferredBlocks() {
+  size_t live_range_count = data()->live_ranges().size();
+  for (size_t i = 0; i < live_range_count; i++) {
+    LiveRange* range = data()->live_ranges()[i];
+    if (range != nullptr && !range->IsEmpty() && !range->spilled() &&
+        !range->IsFixed() && !range->IsChild()) {
+      SplitRangeByClobberingDeferredBlocks(range, data());
+    }
+  }
+}
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8