Remove the fcontext field from all contexts.

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 3610 matching lines @@
     for (int i = 1; i < context_chain_length; i++) {
       movq(dst, Operand(dst, Context::SlotOffset(Context::PREVIOUS_INDEX)));
     }
   } else {
     // Slot is in the current function context.  Move it into the
     // destination register in case we store into it (the write barrier
     // cannot be allowed to destroy the context in rsi).
     movq(dst, rsi);
   }
 
-  // We should not have found a 'with' context by walking the context chain
-  // (i.e., the static scope chain and runtime context chain do not agree).
-  // A variable occurring in such a scope should have slot type LOOKUP and
-  // not CONTEXT.
+  // We should not have found a with or catch context by walking the context
+  // chain (i.e., the static scope chain and runtime context chain do not
+  // agree).  A variable occurring in such a scope should have slot type
+  // LOOKUP and not CONTEXT.
   if (emit_debug_code()) {
-    cmpq(dst, Operand(dst, Context::SlotOffset(Context::FCONTEXT_INDEX)));
-    Check(equal, "Yo dawg, I heard you liked function contexts "
-                 "so I put function contexts in all your contexts");
+    CompareRoot(FieldOperand(dst, HeapObject::kMapOffset),
+                Heap::kWithContextMapRootIndex);
+    Check(not_equal, "Variable resolved to with context.");
+    CompareRoot(FieldOperand(dst, HeapObject::kMapOffset),
+                Heap::kCatchContextMapRootIndex);
+    Check(not_equal, "Variable resolved to catch context.");
   }
 }
 
 #ifdef _WIN64
 static const int kRegisterPassedArguments = 4;
 #else
 static const int kRegisterPassedArguments = 6;
 #endif
 
 void MacroAssembler::LoadGlobalFunction(int index, Register function) {
@@ skipping 94 matching lines @@
   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