Remove broken %_Log functionality.

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 2eb74e55f0c9f71103c351cb92c7fac06028e659..17db9bf1a50205d8a4d002c83042d291151ce23c 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -542,14 +542,6 @@ bool MacroAssembler::AllowThisStubCall(CodeStub* stub) {
 }
 
 
-void MacroAssembler::IllegalOperation(int num_arguments) {
-  if (num_arguments > 0) {
-    addp(rsp, Immediate(num_arguments * kPointerSize));
-  }
-  LoadRoot(rax, Heap::kUndefinedValueRootIndex);
-}
-
-
 void MacroAssembler::IndexFromHash(Register hash, Register index) {
   // The assert checks that the constants for the maximum number of digits
   // for an array index cached in the hash field and the number of bits
@@ -575,10 +567,7 @@ void MacroAssembler::CallRuntime(const Runtime::Function* f,
   // If the expected number of arguments of the runtime function is
   // constant, we check that the actual number of arguments match the
   // expectation.
-  if (f->nargs >= 0 && f->nargs != num_arguments) {
-    IllegalOperation(num_arguments);
-    return;
-  }
+  CHECK(f->nargs < 0 || f->nargs == num_arguments);
 
   // TODO(1236192): Most runtime routines don't need the number of
   // arguments passed in because it is constant. At some point we