Optimize testing for an index's existence in packed Arrays

src/x64/full-codegen-x64.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_X64
 
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
@@ skipping 4322 matching lines @@
   DCHECK(expr->arguments()->length() == 0);
   ExternalReference debug_is_active =
       ExternalReference::debug_is_active_address(isolate());
   __ Move(kScratchRegister, debug_is_active);
   __ movzxbp(rax, Operand(kScratchRegister, 0));
   __ Integer32ToSmi(rax, rax);
   context()->Plug(rax);
 }
 
 
+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);
+
+  __ JumpIfSmi(rax, if_false);
+  __ movp(rax, FieldOperand(rax, HeapObject::kMapOffset));
+  __ movzxbl(rax, FieldOperand(rax, Map::kBitField2Offset));
+  __ shrp(rax, Immediate(Map::ElementsKindBits::kShift));
+  __ cmpb(rax, Immediate(FAST_SMI_ELEMENTS));
+  __ j(equal, if_true);
+  __ cmpb(rax, Immediate(FAST_ELEMENTS));
+  __ j(equal, if_true);
+  __ cmpb(rax, Immediate(FAST_DOUBLE_ELEMENTS));
+  PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
+  Split(equal, 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 839 matching lines @@
   DCHECK_EQ(isolate->builtins()->OsrAfterStackCheck()->entry(),
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64