Splits up dependent load in update of allocation stats.

runtime/vm/stub_code_arm.cc

Index: runtime/vm/stub_code_arm.cc
===================================================================
--- runtime/vm/stub_code_arm.cc	(revision 40840)
+++ runtime/vm/stub_code_arm.cc	(working copy)
@@ -697,26 +697,27 @@
 
   // Successfully allocated the object(s), now update top to point to
   // next object start and initialize the object.
+  __ LoadAllocationStatsAddress(R3, cid, space);
   __ str(R7, Address(R6, 0));
   __ add(R0, R0, Operand(kHeapObjectTag));
-  __ UpdateAllocationStatsWithSize(cid, R8, R4, space);
 
   // Initialize the tags.
   // R0: new object start as a tagged pointer.
+  // R3: allocation stats address.
   // R7: new object end address.
   // R8: allocation size.
   {
     const intptr_t shift = RawObject::kSizeTagPos - kObjectAlignmentLog2;
 
     __ CompareImmediate(R8, RawObject::SizeTag::kMaxSizeTag);
-    __ mov(R8, Operand(R8, LSL, shift), LS);
-    __ mov(R8, Operand(0), HI);
+    __ mov(R6, Operand(R8, LSL, shift), LS);
+    __ mov(R6, Operand(0), HI);
 
     // Get the class index and insert it into the tags.
-    // R8: size and bit tags.
+    // R6: size and bit tags.
     __ LoadImmediate(TMP, RawObject::ClassIdTag::encode(cid));
-    __ orr(R8, R8, Operand(TMP));
-    __ str(R8, FieldAddress(R0, Array::tags_offset()));  // Store tags.
+    __ orr(R6, R6, Operand(TMP));
+    __ str(R6, FieldAddress(R0, Array::tags_offset()));  // Store tags.
   }
 
   // R0: new object start as a tagged pointer.
@@ -733,20 +734,24 @@
 
   // Initialize all array elements to raw_null.
   // R0: new object start as a tagged pointer.
+  // R3: allocation stats address.
   // R7: new object end address.
   // R8: iterator which initially points to the start of the variable
   // data area to be initialized.
-  // R3: null
-  __ LoadImmediate(R3, reinterpret_cast<intptr_t>(Object::null()));
+  // R4, R5: null
+  __ LoadImmediate(R4, reinterpret_cast<intptr_t>(Object::null()));
+  __ mov(R5, Operand(R4));
   __ AddImmediate(R8, R0, sizeof(RawArray) - kHeapObjectTag);
 
   Label init_loop;
   __ Bind(&init_loop);
+  __ AddImmediate(R8, 2 * kWordSize);
   __ cmp(R8, Operand(R7));
-  __ str(R3, Address(R8, 0), CC);
-  __ AddImmediate(R8, kWordSize, CC);
+  __ strd(R4, Address(R8, -2 * kWordSize), LS);
   __ b(&init_loop, CC);
+  __ str(R4, Address(R8, -2 * kWordSize), HI);
 
+  __ IncrementAllocationStatsWithSize(R3, R8, cid, space);
   __ Ret();  // Returns the newly allocated object in R0.
   // Unable to allocate the array using the fast inline code, just call
   // into the runtime.
@@ -938,6 +943,7 @@
     // R1: number of context variables.
     // R2: object size.
     // R3: potential next object start.
+    // R5: top address.
     __ LoadImmediate(IP, heap->EndAddress(space));
     __ ldr(IP, Address(IP, 0));
     __ cmp(R3, Operand(IP));
@@ -953,56 +959,68 @@
     // R1: number of context variables.
     // R2: object size.
     // R3: next object start.
+    // R5: top address.
+    __ LoadAllocationStatsAddress(R4, cid, space);
     __ str(R3, Address(R5, 0));
     __ add(R0, R0, Operand(kHeapObjectTag));
-    __ UpdateAllocationStatsWithSize(cid, R2, R5, space);
 
     // Calculate the size tag.
     // R0: new object.
     // R1: number of context variables.
     // R2: object size.
+    // R4: allocation stats address.
     const intptr_t shift = RawObject::kSizeTagPos - kObjectAlignmentLog2;
     __ CompareImmediate(R2, RawObject::SizeTag::kMaxSizeTag);
     // If no size tag overflow, shift R2 left, else set R2 to zero.
-    __ mov(R2, Operand(R2, LSL, shift), LS);
-    __ mov(R2, Operand(0), HI);
+    __ mov(R3, Operand(R2, LSL, shift), LS);
+    __ mov(R3, Operand(0), HI);
 
     // Get the class index and insert it into the tags.
-    // R2: size and bit tags.
+    // R3: size and bit tags.
     __ LoadImmediate(IP, RawObject::ClassIdTag::encode(cid));
-    __ orr(R2, R2, Operand(IP));
-    __ str(R2, FieldAddress(R0, Context::tags_offset()));
+    __ orr(R3, R3, Operand(IP));
+    __ str(R3, FieldAddress(R0, Context::tags_offset()));
 
     // Setup up number of context variables field.
     // R0: new object.
     // R1: number of context variables as integer value (not object).
+    // R2: object size.
+    // R4: allocation stats address.
     __ str(R1, FieldAddress(R0, Context::num_variables_offset()));
 
     // Setup isolate field.
-    // Load Isolate pointer into R2.
+    // Load Isolate pointer into R3.
     // R0: new object.
     // R1: number of context variables.
-    __ LoadIsolate(R2);
-    // R2: isolate, not an object.
-    __ str(R2, FieldAddress(R0, Context::isolate_offset()));
+    // R2: object size.
+    // R4: allocation stats address.
+    __ LoadIsolate(R3);
+    // R3: isolate, not an object.
+    __ str(R3, FieldAddress(R0, Context::isolate_offset()));
 
     // Setup the parent field.
     // R0: new object.
     // R1: number of context variables.
-    __ LoadImmediate(R2, reinterpret_cast<intptr_t>(Object::null()));
-    __ str(R2, FieldAddress(R0, Context::parent_offset()));
+    // R2: object size.
+    // R4: allocation stats address.
+    __ LoadImmediate(R3, reinterpret_cast<intptr_t>(Object::null()));
+    __ str(R3, FieldAddress(R0, Context::parent_offset()));
 
     // Initialize the context variables.
     // R0: new object.
     // R1: number of context variables.
-    // R2: raw null.
+    // R2: object size.
+    // R3: raw null.
+    // R4: allocation stats address.
     Label loop;
-    __ AddImmediate(R3, R0, Context::variable_offset(0) - kHeapObjectTag);
+    __ AddImmediate(R5, R0, Context::variable_offset(0) - kHeapObjectTag);
     __ Bind(&loop);
     __ subs(R1, R1, Operand(1));
-    __ str(R2, Address(R3, R1, LSL, 2), PL);  // Store if R1 positive or zero.
+    __ str(R3, Address(R5, R1, LSL, 2), PL);  // Store if R1 positive or zero.
     __ b(&loop, NE);  // Loop if R1 not zero.
 
+    __ IncrementAllocationStatsWithSize(R4, R2, cid, space);
+
     // Done allocating and initializing the context.
     // R0: new object.
     __ Ret();
@@ -1108,15 +1126,10 @@
   const int kInlineInstanceSize = 12;
   const intptr_t instance_size = cls.instance_size();
   ASSERT(instance_size > 0);
-  if (is_cls_parameterized) {
-    __ ldr(R1, Address(SP, 0));
-    // R1: instantiated type arguments.
-  }
   if (FLAG_inline_alloc && Heap::IsAllocatableInNewSpace(instance_size)) {
     Label slow_case;
     // Allocate the object and update top to point to
     // next object start and initialize the allocated object.
-    // R1: instantiated type arguments (if is_cls_parameterized).
     Heap* heap = Isolate::Current()->heap();
     Heap::Space space = heap->SpaceForAllocation(cls.id());
     __ LoadImmediate(R5, heap->TopAddress(space));
@@ -1134,11 +1147,14 @@
       __ b(&slow_case, CS);  // Unsigned higher or equal.
     }
     __ str(R3, Address(R5, 0));
-    __ UpdateAllocationStats(cls.id(), R5, space);
 
+    // Load the address of the allocation stats table. We split up the load
+    // and the increment so that the dependent load is not too nearby.
+    __ LoadAllocationStatsAddress(R5, cls.id(), space);
+
     // R2: new object start.
     // R3: next object start.
-    // R1: new object type arguments (if is_cls_parameterized).
+    // R5: allocation stats table.
     // Set the tags.
     uword tags = 0;
     tags = RawObject::SizeTag::update(instance_size, tags);
@@ -1153,49 +1169,69 @@
     // R0: raw null.
     // R2: new object start.
     // R3: next object start.
-    // R1: new object type arguments (if is_cls_parameterized).
+    // R5: allocation stats table.
     // First try inlining the initialization without a loop.
     if (instance_size < (kInlineInstanceSize * kWordSize)) {
       // Check if the object contains any non-header fields.
       // Small objects are initialized using a consecutive set of writes.
-      for (intptr_t current_offset = Instance::NextFieldOffset();
-           current_offset < instance_size;
-           current_offset += kWordSize) {
+      intptr_t current_offset = Instance::NextFieldOffset();
+      // Write two nulls at a time.
+      if (instance_size >= 2 * kWordSize) {
+        __ mov(R1, Operand(R0));
+        while (current_offset + kWordSize < instance_size) {
+          __ StoreToOffset(kWordPair, R0, R2, current_offset);
+          current_offset += 2 * kWordSize;
+        }
+      }
+      // Write remainder.
+      while (current_offset < instance_size) {
         __ StoreToOffset(kWord, R0, R2, current_offset);
+        current_offset += kWordSize;
       }
     } else {
+      // There are more than kInlineInstanceSize(12) fields
       __ add(R4, R2, Operand(Instance::NextFieldOffset()));
+      __ mov(R1, Operand(R0));
       // Loop until the whole object is initialized.
       // R0: raw null.
+      // R1: raw null.
       // R2: new object.
       // R3: next object start.
       // R4: next word to be initialized.
-      // R1: new object type arguments (if is_cls_parameterized).
+      // R5: allocation stats table.
       Label init_loop;
-      Label done;
       __ Bind(&init_loop);
+      __ AddImmediate(R4, 2 * kWordSize);
       __ cmp(R4, Operand(R3));
-      __ b(&done, CS);
-      __ str(R0, Address(R4, 0));
-      __ AddImmediate(R4, kWordSize);
-      __ b(&init_loop);
-      __ Bind(&done);
+      __ strd(R0, Address(R4, -2 * kWordSize), LS);
+      __ b(&init_loop, CC);
+      __ str(R0, Address(R4, -2 * kWordSize), HI);
     }
     if (is_cls_parameterized) {
-      // R1: new object type arguments.
       // Set the type arguments in the new object.
-      __ StoreToOffset(kWord, R1, R2, cls.type_arguments_field_offset());
+      __ ldr(R4, Address(SP, 0));
+      __ StoreToOffset(kWord, R4, R2, cls.type_arguments_field_offset());
     }
+
     // Done allocating and initializing the instance.
     // R2: new object still missing its heap tag.
+    // R5: allocation stats table.
     __ add(R0, R2, Operand(kHeapObjectTag));
+
+    // Update allocation stats.
+    __ IncrementAllocationStats(R5, cls.id(), space);
+
     // R0: new object.
     __ Ret();
 
     __ Bind(&slow_case);
   }
+  if (is_cls_parameterized) {
+    // Load the type arguments.
+    __ ldr(R4, Address(SP, 0));
+  }
   // If is_cls_parameterized:
-  // R1: new object type arguments.
+  // R4: new object type arguments.
   // Create a stub frame as we are pushing some objects on the stack before
   // calling into the runtime.
   __ EnterStubFrame(true);  // Uses pool pointer to pass cls to runtime.
@@ -1204,7 +1240,7 @@
   __ PushObject(cls);  // Push class of object to be allocated.
   if (is_cls_parameterized) {
     // Push type arguments.
-    __ Push(R1);
+    __ Push(R4);
   } else {
     // Push null type arguments.
     __ Push(R2);