Improve code (less code, slightly faster) for polymorphic calls, by loading the argument descriptor…

runtime/vm/code_patcher_x64.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/assembler.h"
 #include "vm/code_patcher.h"
 #include "vm/cpu.h"
@@ skipping 68 matching lines @@
 
   RawObject* ic_data() const { return immediate_one(); }
   RawObject* arguments_descriptor() const { return immediate_two(); }
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(InstanceCall);
 };
 
 
 // The expected pattern of a dart static call:
-//  mov R10, arguments_descriptor_array (10 bytes)
+//  mov R10, arguments_descriptor_array (10 bytes) (optional in polym. calls)
 //  mov R11, target_address (10 bytes)
 //  call R11  (3 bytes)
 //  <- return address
 class StaticCall : public ValueObject {
  public:
   explicit StaticCall(uword return_address)
       : start_(return_address - kCallPatternSize) {
     ASSERT(IsValid(return_address));
-    ASSERT((kCallPatternSize - 10) == Assembler::kCallExternalLabelSize);
+    ASSERT(kCallPatternSize == Assembler::kCallExternalLabelSize);
   }
 
-  static const int kCallPatternSize = 23;
+  static const int kCallPatternSize = 13;
 
   static bool IsValid(uword return_address) {
     uint8_t* code_bytes =
         reinterpret_cast<uint8_t*>(return_address - kCallPatternSize);
-    return (code_bytes[00] == 0x49) && (code_bytes[01] == 0xBA) &&
-           (code_bytes[10] == 0x49) && (code_bytes[11] == 0xBB) &&
-           (code_bytes[20] == 0x41) && (code_bytes[21] == 0xFF) &&
-           (code_bytes[22] == 0xD3);
+    return (code_bytes[00] == 0x49) && (code_bytes[01] == 0xBB) &&
+           (code_bytes[10] == 0x41) && (code_bytes[11] == 0xFF) &&
+           (code_bytes[12] == 0xD3);
   }
 
   uword target() const {
-    return *reinterpret_cast<uword*>(start_ + 10 + 2);
+    return *reinterpret_cast<uword*>(start_ + 2);
   }
 
   void set_target(uword target) const {
-    uword* target_addr = reinterpret_cast<uword*>(start_ + 10 + 2);
+    uword* target_addr = reinterpret_cast<uword*>(start_ + 2);
     *target_addr = target;
-    CPU::FlushICache(start_ + 10, 2 + 8);
+    CPU::FlushICache(start_, 2 + 8);
   }
 
  private:
   uword start_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(StaticCall);
 };
 
 
 uword CodePatcher::GetStaticCallTargetAt(uword return_address,
@@ skipping 47 matching lines @@
   *reinterpret_cast<uint8_t*>(start) = 0xE8;
   ShortCallPattern call(start);
   call.SetTargetAddress(target);
   CPU::FlushICache(start, ShortCallPattern::InstructionLength());
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64