Only pass isolate parameter to C helper functions that need it.

src/x64/macro-assembler-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2833 matching lines @@
   return num_arguments - kRegisterPassedArguments;
 #endif
 }
 
 
 void MacroAssembler::PrepareCallCFunction(int num_arguments) {
   int frame_alignment = OS::ActivationFrameAlignment();
   ASSERT(frame_alignment != 0);
   ASSERT(num_arguments >= 0);
 
-  // Reserve space for Isolate address which is always passed as last parameter
-  num_arguments += 1;
-
   // Make stack end at alignment and allocate space for arguments and old rsp.
   movq(kScratchRegister, rsp);
   ASSERT(IsPowerOf2(frame_alignment));
   int argument_slots_on_stack =
       ArgumentStackSlotsForCFunctionCall(num_arguments);
   subq(rsp, Immediate((argument_slots_on_stack + 1) * kPointerSize));
   and_(rsp, Immediate(-frame_alignment));
   movq(Operand(rsp, argument_slots_on_stack * kPointerSize), kScratchRegister);
 }
 
 
 void MacroAssembler::CallCFunction(ExternalReference function,
                                    int num_arguments) {
   LoadAddress(rax, function);
   CallCFunction(rax, num_arguments);
 }
 
 
 void MacroAssembler::CallCFunction(Register function, int num_arguments) {
-  // Pass current isolate address as additional parameter.
-  if (num_arguments < kRegisterPassedArguments) {
-#ifdef _WIN64
-    // First four arguments are passed in registers on Windows.
-    Register arg_to_reg[] = {rcx, rdx, r8, r9};
-#else
-    // First six arguments are passed in registers on other platforms.
-    Register arg_to_reg[] = {rdi, rsi, rdx, rcx, r8, r9};
-#endif
-    Register reg = arg_to_reg[num_arguments];
-    LoadAddress(reg, ExternalReference::isolate_address());
-  } else {
-    // Push Isolate pointer after all parameters.
-    int argument_slots_on_stack =
-        ArgumentStackSlotsForCFunctionCall(num_arguments);
-    LoadAddress(kScratchRegister, ExternalReference::isolate_address());
-    movq(Operand(rsp, argument_slots_on_stack * kPointerSize),
-         kScratchRegister);
-  }
-
   // Check stack alignment.
   if (emit_debug_code()) {
     CheckStackAlignment();
   }
 
   call(function);
   ASSERT(OS::ActivationFrameAlignment() != 0);
   ASSERT(num_arguments >= 0);
-  num_arguments += 1;
   int argument_slots_on_stack =
       ArgumentStackSlotsForCFunctionCall(num_arguments);
   movq(rsp, Operand(rsp, argument_slots_on_stack * kPointerSize));
 }
 
 
 CodePatcher::CodePatcher(byte* address, int size)
     : address_(address), size_(size), masm_(address, size + Assembler::kGap) {
   // Create a new macro assembler pointing to the address of the code to patch.
   // The size is adjusted with kGap on order for the assembler to generate size
   // bytes of instructions without failing with buffer size constraints.
   ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
 }
 
 
 CodePatcher::~CodePatcher() {
   // Indicate that code has changed.
   CPU::FlushICache(address_, size_);
 
   // Check that the code was patched as expected.
   ASSERT(masm_.pc_ == address_ + size_);
   ASSERT(masm_.reloc_info_writer.pos() == address_ + size_ + Assembler::kGap);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64