Port FastNewContextStub to x64 and arm.

src/arm/codegen-arm.cc

Index: src/arm/codegen-arm.cc
===================================================================
--- src/arm/codegen-arm.cc	(revision 3582)
+++ src/arm/codegen-arm.cc	(working copy)
@@ -187,12 +187,18 @@
     function_return_is_shadowed_ = false;
 
     VirtualFrame::SpilledScope spilled_scope;
-    if (scope_->num_heap_slots() > 0) {
+    int heap_slots = scope_->num_heap_slots();
+    if (heap_slots > 0) {
       // Allocate local context.
       // Get outer context and create a new context based on it.
       __ ldr(r0, frame_->Function());
       frame_->EmitPush(r0);
-      frame_->CallRuntime(Runtime::kNewContext, 1);  // r0 holds the result
+      if (heap_slots <= FastNewContextStub::kMaximumSlots) {
+        FastNewContextStub stub(heap_slots);
+        frame_->CallStub(&stub, 1);
+      } else {
+        frame_->CallRuntime(Runtime::kNewContext, 1);
+      }
 
 #ifdef DEBUG
       JumpTarget verified_true;
@@ -4432,6 +4438,55 @@
 }
 
 
+void FastNewContextStub::Generate(MacroAssembler* masm) {
+  // Try to allocate the context in new space.
+  Label gc;
+  int length = slots_ + Context::MIN_CONTEXT_SLOTS;
+
+  // Pop the function from the stack.
+  __ pop(r3);
+
+  // Attempt to allocate the context in new space.
+  __ AllocateInNewSpace(length + (FixedArray::kHeaderSize / kPointerSize),
+                        r0,
+                        r1,
+                        r2,
+                        &gc,
+                        TAG_OBJECT);
+
+  // Setup the object header.
+  __ LoadRoot(r2, Heap::kContextMapRootIndex);
+  __ str(r2, FieldMemOperand(r0, HeapObject::kMapOffset));
+  __ mov(r2, Operand(length));
+  __ str(r2, FieldMemOperand(r0, Array::kLengthOffset));
+
+  // Setup the fixed slots.
+  __ mov(r1, Operand(Smi::FromInt(0)));
+  __ str(r3, MemOperand(r0, Context::SlotOffset(Context::CLOSURE_INDEX)));
+  __ str(r0, MemOperand(r0, Context::SlotOffset(Context::FCONTEXT_INDEX)));
+  __ str(r1, MemOperand(r0, Context::SlotOffset(Context::PREVIOUS_INDEX)));
+  __ str(r1, MemOperand(r0, Context::SlotOffset(Context::EXTENSION_INDEX)));
+
+  // Copy the global object from the surrounding context.
+  __ ldr(r1, MemOperand(cp, Context::SlotOffset(Context::GLOBAL_INDEX)));
+  __ str(r1, MemOperand(r0, Context::SlotOffset(Context::GLOBAL_INDEX)));
+
+  // Initialize the rest of the slots to undefined.
+  __ LoadRoot(r1, Heap::kUndefinedValueRootIndex);
+  for (int i = Context::MIN_CONTEXT_SLOTS; i < length; i++) {
+    __ str(r1, MemOperand(r0, Context::SlotOffset(i)));
+  }
+
+  // Return. The on-stack parameter has already been popped.
+  __ mov(cp, r0);
+  __ Ret();
+
+  // Need to collect. Call into runtime system.
+  __ bind(&gc);
+  __ TailCallRuntime(ExternalReference(Runtime::kNewContext), 1, 1);
+}
+
+
 // Count leading zeros in a 32 bit word.  On ARM5 and later it uses the clz
 // instruction.  On pre-ARM5 hardware this routine gives the wrong answer for 0
 // (31 instead of 32).