Optimize testing for an index's existence in packed Arrays

src/arm/full-codegen-arm.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 "src/v8.h"
 
 #if V8_TARGET_ARCH_ARM
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 4360 matching lines @@
   DCHECK(expr->arguments()->length() == 0);
   ExternalReference debug_is_active =
       ExternalReference::debug_is_active_address(isolate());
   __ mov(ip, Operand(debug_is_active));
   __ ldrb(r0, MemOperand(ip));
   __ SmiTag(r0);
   context()->Plug(r0);
 }
 
 
+void FullCodeGenerator::EmitHasFastPackedElements(CallRuntime* expr) {
+  ZoneList<Expression*>* args = expr->arguments();
+  DCHECK(args->length() == 1);
+
+  VisitForAccumulatorValue(args->at(0));
+
+  Label materialize_true, materialize_false;
+  Label* if_true = NULL;
+  Label* if_false = NULL;
+  Label* fall_through = NULL;
+  context()->PrepareTest(&materialize_true, &materialize_false, &if_true,
+                         &if_false, &fall_through);
+
+  Register object = r0;
+  Register map = r1;
+  Register elements_kind = r2;
+
+  __ JumpIfSmi(object, if_false);
+  __ ldr(map, FieldMemOperand(object, HeapObject::kMapOffset));
+  __ ldrb(elements_kind, FieldMemOperand(map, Map::kBitField2Offset));
+  __ mov(elements_kind,
+         Operand(elements_kind, LSR, Map::ElementsKindBits::kShift));
+  __ cmp(elements_kind, Operand(FAST_SMI_ELEMENTS));
+  __ b(eq, if_true);
+  __ cmp(elements_kind, Operand(FAST_ELEMENTS));
+  __ b(eq, if_true);
+  __ cmp(elements_kind, Operand(FAST_DOUBLE_ELEMENTS));
+  PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
+  Split(eq, if_true, if_false, fall_through);
+
+  context()->Plug(if_true, if_false);
+}
+
+
 void FullCodeGenerator::VisitCallRuntime(CallRuntime* expr) {
   if (expr->function() != NULL &&
       expr->function()->intrinsic_type == Runtime::INLINE) {
     Comment cmnt(masm_, "[ InlineRuntimeCall");
     EmitInlineRuntimeCall(expr);
     return;
   }
 
   Comment cmnt(masm_, "[ CallRuntime");
   ZoneList<Expression*>* args = expr->arguments();
@@ skipping 907 matching lines @@
 
   DCHECK(interrupt_address ==
          isolate->builtins()->OsrAfterStackCheck()->entry());
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM