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

src/ia32/macro-assembler-ia32.cc

Index: src/ia32/macro-assembler-ia32.cc
diff --git a/src/ia32/macro-assembler-ia32.cc b/src/ia32/macro-assembler-ia32.cc
index ba30c49ced678c18fcc4658323e9ff779e38ecd6..21315378c38eb25be1392499cc4f31b2b996865b 100644
--- a/src/ia32/macro-assembler-ia32.cc
+++ b/src/ia32/macro-assembler-ia32.cc
@@ -1988,17 +1988,14 @@ void MacroAssembler::JumpIfNotBothSequentialAsciiStrings(Register object1,
 
 
 void MacroAssembler::PrepareCallCFunction(int num_arguments, Register scratch) {
-  // Reserve space for Isolate address which is always passed as last parameter
-  num_arguments += 1;
-
-  int frameAlignment = OS::ActivationFrameAlignment();
-  if (frameAlignment != 0) {
+  int frame_alignment = OS::ActivationFrameAlignment();
+  if (frame_alignment != 0) {
     // Make stack end at alignment and make room for num_arguments words
     // and the original value of esp.
     mov(scratch, esp);
     sub(Operand(esp), Immediate((num_arguments + 1) * kPointerSize));
-    ASSERT(IsPowerOf2(frameAlignment));
-    and_(esp, -frameAlignment);
+    ASSERT(IsPowerOf2(frame_alignment));
+    and_(esp, -frame_alignment);
     mov(Operand(esp, num_arguments * kPointerSize), scratch);
   } else {
     sub(Operand(esp), Immediate(num_arguments * kPointerSize));
@@ -2016,11 +2013,6 @@ void MacroAssembler::CallCFunction(ExternalReference function,
 
 void MacroAssembler::CallCFunction(Register function,
                                    int num_arguments) {
-  // Pass current isolate address as additional parameter.
-  mov(Operand(esp, num_arguments * kPointerSize),
-      Immediate(ExternalReference::isolate_address()));
-  num_arguments += 1;
-
   // Check stack alignment.
   if (emit_debug_code()) {
     CheckStackAlignment();
@@ -2030,7 +2022,7 @@ void MacroAssembler::CallCFunction(Register function,
   if (OS::ActivationFrameAlignment() != 0) {
     mov(esp, Operand(esp, num_arguments * kPointerSize));
   } else {
-    add(Operand(esp), Immediate(num_arguments * sizeof(int32_t)));
+    add(Operand(esp), Immediate(num_arguments * kPointerSize));
   }
 }