Folding of bounded dynamic size allocations with const size allocations.

src/hydrogen-instructions.cc

 // Copyright 2012 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 "v8.h"
 
 #include "double.h"
 #include "factory.h"
 #include "hydrogen-infer-representation.h"
 #include "property-details-inl.h"
@@ skipping 3724 matching lines @@
   // Check whether we are folding within the same block for local folding.
   if (FLAG_use_local_allocation_folding && dominator->block() != block()) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s), crosses basic blocks\n",
           id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
     }
     return false;
   }
 
   HAllocate* dominator_allocate = HAllocate::cast(dominator);
-  HValue* dominator_size = dominator_allocate->size();
-  HValue* current_size = size();
-
-  // TODO(hpayer): Add support for non-constant allocation in dominator.
-  if (!dominator_size->IsInteger32Constant()) {
-    if (FLAG_trace_allocation_folding) {
-      PrintF("#%d (%s) cannot fold into #%d (%s), "
-             "dynamic allocation size in dominator\n",
-          id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
-    }
-    return false;
-  }
 
   dominator_allocate = GetFoldableDominator(dominator_allocate);
   if (dominator_allocate == NULL) {
     return false;
   }
 
-  if (!has_size_upper_bound()) {
+  if (!has_size_upper_bound() || !dominator_allocate->has_size_upper_bound()) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s), "
              "can't estimate total allocation size\n",
           id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
     }
     return false;
   }
 
+  HValue* dominator_size = dominator_allocate->size();
+  // TODO(ishell): support folding of dynamic size allocation with
+  // double aligned allocation.
+  if (!dominator_size->IsInteger32Constant() && MustAllocateDoubleAligned()) {
+    if (FLAG_trace_allocation_folding) {
+      PrintF("#%d (%s) cannot fold into #%d (%s), dynamic size "
+             "in dominator and double aligned requirement\n",
+          id(), Mnemonic(), dominator->id(), dominator->Mnemonic());
+    }
+    return false;
+  }
+
+  HValue* current_size = size();
   if (!current_size->IsInteger32Constant()) {
     // If it's not constant then it is a size_in_bytes calculation graph
     // like this: (const_header_size + const_element_size * size).
     ASSERT(current_size->IsInstruction());
 
     HInstruction* current_instr = HInstruction::cast(current_size);
     if (!current_instr->Dominates(dominator_allocate)) {
       if (FLAG_trace_allocation_folding) {
         PrintF("#%d (%s) cannot fold into #%d (%s), dynamic size "
                "value does not dominate target allocation\n",
             id(), Mnemonic(), dominator_allocate->id(),
             dominator_allocate->Mnemonic());
       }
       return false;
     }
   }
 
   ASSERT((IsNewSpaceAllocation() &&
          dominator_allocate->IsNewSpaceAllocation()) ||
          (IsOldDataSpaceAllocation() &&
          dominator_allocate->IsOldDataSpaceAllocation()) ||
          (IsOldPointerSpaceAllocation() &&
          dominator_allocate->IsOldPointerSpaceAllocation()));
 
-  // First update the size of the dominator allocate instruction.
-  dominator_size = dominator_allocate->size();
-  int32_t original_object_size =
-      HConstant::cast(dominator_size)->GetInteger32Constant();
-  int32_t dominator_size_constant = original_object_size;
+  // First update the size and size upper bound of the dominator allocate
+  // instruction.
+  int32_t dominator_size_upper_bound =
+      dominator_allocate->size_upper_bound()->GetInteger32Constant();
 
   if (MustAllocateDoubleAligned()) {
-    if ((dominator_size_constant & kDoubleAlignmentMask) != 0) {
-      dominator_size_constant += kDoubleSize / 2;
+    if ((dominator_size_upper_bound & kDoubleAlignmentMask) != 0) {
+      dominator_size_upper_bound += kDoubleSize / 2;
     }
   }
 
-  int32_t current_size_max_value = size_upper_bound()->GetInteger32Constant();
-  int32_t new_dominator_size = dominator_size_constant + current_size_max_value;
+  int32_t current_size_upper_bound = size_upper_bound()->GetInteger32Constant();
+  int32_t new_dominator_size_upper_bound =
+      dominator_size_upper_bound + current_size_upper_bound;
 
   // Since we clear the first word after folded memory, we cannot use the
   // whole Page::kMaxRegularHeapObjectSize memory.
-  if (new_dominator_size > Page::kMaxRegularHeapObjectSize - kPointerSize) {
+  if (new_dominator_size_upper_bound >
+      Page::kMaxRegularHeapObjectSize - kPointerSize) {
     if (FLAG_trace_allocation_folding) {
       PrintF("#%d (%s) cannot fold into #%d (%s) due to size: %d\n",
           id(), Mnemonic(), dominator_allocate->id(),
-          dominator_allocate->Mnemonic(), new_dominator_size);
+          dominator_allocate->Mnemonic(), new_dominator_size_upper_bound);
     }
     return false;
   }
 
-  HInstruction* new_dominator_size_value;
-
-  if (current_size->IsInteger32Constant()) {
-    new_dominator_size_value =
+  HValue* aligned_dominator_size;
+  if (dominator_size->IsInteger32Constant()) {
+    aligned_dominator_size =
         HConstant::CreateAndInsertBefore(zone,
                                          context(),
-                                         new_dominator_size,
-                                         Representation::None(),
-                                         dominator_allocate);
-  } else {
-    HValue* new_dominator_size_constant =
-        HConstant::CreateAndInsertBefore(zone,
-                                         context(),
-                                         dominator_size_constant,
+                                         dominator_size_upper_bound,
                                          Representation::Integer32(),
                                          dominator_allocate);
 
+  } else {
+    aligned_dominator_size = dominator_size;
+  }
+
+  HConstant* new_dominator_size_upper_bound_c =

[Hannes Payer (out of office), 2014/06/04 09:44:29]

I don't like the _c, can we have a proper name?

Moreover, the size variable names are very confusing and inconsistent. Can we
clean that up?

I think the start point is good:
dominator_size is the dominator size instruction, the new dominator size
instruction should be called new_dominator_size. When we take the int value of a
constant size instruction it could be called dominator_size_value...

[Igor Sheludko, 2014/06/04 10:07:41]

Done.

+      HConstant::CreateAndInsertBefore(zone,
+                                       context(),
+                                       new_dominator_size_upper_bound,
+                                       Representation::None(),
+                                       dominator_allocate);
+
+  HInstruction* new_dominator_size_value;
+  if (current_size->IsInteger32Constant() &&
+      dominator_size->IsInteger32Constant()) {
+    new_dominator_size_value = new_dominator_size_upper_bound_c;
+
+  } else {
     // Add old and new size together and insert.
-    current_size->ChangeRepresentation(Representation::Integer32());
+    if (current_size->IsInteger32Constant()) {
+      // Create a copy of constant and put it into the right place
+      current_size =
+          HConstant::CreateAndInsertBefore(zone,
+                                           context(),
+                                           current_size->GetInteger32Constant(),
+                                           Representation::Integer32(),
+                                           dominator_allocate);
+    } else {
+      current_size->ChangeRepresentation(Representation::Integer32());
+    }
 
     new_dominator_size_value = HAdd::New(zone, context(),
-        new_dominator_size_constant, current_size);
+                                         aligned_dominator_size, current_size);
     new_dominator_size_value->ClearFlag(HValue::kCanOverflow);
     new_dominator_size_value->ChangeRepresentation(Representation::Integer32());
 
     new_dominator_size_value->InsertBefore(dominator_allocate);
   }
 
-  dominator_allocate->UpdateSize(new_dominator_size_value);
+  dominator_allocate->UpdateSize(
+      new_dominator_size_value, new_dominator_size_upper_bound_c);
 
   if (MustAllocateDoubleAligned()) {
     if (!dominator_allocate->MustAllocateDoubleAligned()) {
       dominator_allocate->MakeDoubleAligned();
     }
   }
 
   bool keep_new_space_iterable = FLAG_log_gc || FLAG_heap_stats;
 #ifdef VERIFY_HEAP
   keep_new_space_iterable = keep_new_space_iterable || FLAG_verify_heap;
 #endif
 
   if (keep_new_space_iterable && dominator_allocate->IsNewSpaceAllocation()) {
     dominator_allocate->MakePrefillWithFiller();
   } else {
     // TODO(hpayer): This is a short-term hack to make allocation mementos
     // work again in new space.
-    dominator_allocate->ClearNextMapWord(original_object_size);
+    dominator_allocate->ClearNextMapWord(dominator_size);
   }
 
   dominator_allocate->UpdateClearNextMapWord(MustClearNextMapWord());
 
   // After that replace the dominated allocate instruction.
-  HInstruction* inner_offset = HConstant::CreateAndInsertBefore(
-      zone,
-      context(),
-      dominator_size_constant,
-      Representation::None(),
-      this);
-
   HInstruction* dominated_allocate_instr =
       HInnerAllocatedObject::New(zone,
                                  context(),
                                  dominator_allocate,
-                                 inner_offset,
+                                 aligned_dominator_size,
                                  type());
   dominated_allocate_instr->InsertBefore(this);
   DeleteAndReplaceWith(dominated_allocate_instr);
   if (FLAG_trace_allocation_folding) {
     PrintF("#%d (%s) folded into #%d (%s)\n",
         id(), Mnemonic(), dominator_allocate->id(),
         dominator_allocate->Mnemonic());
   }
   return true;
 }
@@ skipping 106 matching lines @@
                                      FreeSpace::kSizeOffset,
                                      Representation::Smi());
   HStoreNamedField* store_size = HStoreNamedField::New(zone, context(),
       free_space_instr, access, filler_size);
   store_size->SetFlag(HValue::kHasNoObservableSideEffects);
   store_size->InsertAfter(filler_size);
   filler_free_space_size_ = store_size;
 }
 
 
-void HAllocate::ClearNextMapWord(int offset) {
+void HAllocate::ClearNextMapWord(HValue* offset) {
   if (MustClearNextMapWord()) {
     Zone* zone = block()->zone();
-    HObjectAccess access =
-        HObjectAccess::ForObservableJSObjectOffset(offset);
-    HStoreNamedField* clear_next_map =
-        HStoreNamedField::New(zone, context(), this, access,
-            block()->graph()->GetConstant0());
-    clear_next_map->ClearAllSideEffects();
-    clear_next_map->InsertAfter(this);
+
+    if (offset->IsInteger32Constant()) {
+      int offset_value = HConstant::cast(offset)->GetInteger32Constant();
+      HObjectAccess access =
+          HObjectAccess::ForObservableJSObjectOffset(offset_value);
+      HStoreNamedField* clear_next_map =
+          HStoreNamedField::New(zone, context(), this, access,
+                                block()->graph()->GetConstant0());
+      clear_next_map->ClearAllSideEffects();
+      clear_next_map->InsertAfter(this);
+    } else {
+      HStoreKeyed* clear_next_map =
+          HStoreKeyed::New(zone, context(),
+                           this, offset,
+                           block()->graph()->GetConstant0(),
+                           FAST_HOLEY_SMI_ELEMENTS);
+      clear_next_map->ClearAllSideEffects();
+      clear_next_map->InsertAfter(this);

[Hannes Payer (out of office), 2014/06/04 09:44:29]

Can you move
clear_next_map->ClearAllSideEffects();
clear_next_map->InsertAfter(this);
after the else case?

[Igor Sheludko, 2014/06/04 10:07:41]

Done.

+    }
   }
 }
 
 
 void HAllocate::PrintDataTo(StringStream* stream) {
   size()->PrintNameTo(stream);
   stream->Add(" (");
   if (IsNewSpaceAllocation()) stream->Add("N");
   if (IsOldPointerSpaceAllocation()) stream->Add("P");
   if (IsOldDataSpaceAllocation()) stream->Add("D");
@@ skipping 780 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal