Enable optimization of functions with generic switches.

src/x64/full-codegen-x64.cc

 // Copyright 2012 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 968 matching lines @@
       __ jmp(clause->body_target());
       __ bind(&slow_case);
     }
 
     // Record position before stub call for type feedback.
     SetSourcePosition(clause->position());
     Handle<Code> ic = CompareIC::GetUninitialized(isolate(), Token::EQ_STRICT);
     CallIC(ic, RelocInfo::CODE_TARGET, clause->CompareId());
     patch_site.EmitPatchInfo();
 
+    Label skip;
+    __ jmp(&skip, Label::kNear);
+    PrepareForBailout(clause, TOS_REG);
+    __ CompareRoot(rax, Heap::kTrueValueRootIndex);
+    __ j(not_equal, &next_test);
+    __ Drop(1);
+    __ jmp(clause->body_target());
+    __ bind(&skip);
+
     __ testq(rax, rax);
     __ j(not_equal, &next_test);
     __ Drop(1);  // Switch value is no longer needed.
     __ jmp(clause->body_target());
   }
 
   // Discard the test value and jump to the default if present, otherwise to
   // the end of the statement.
   __ bind(&next_test);
   __ Drop(1);  // Switch value is no longer needed.
@@ skipping 3895 matching lines @@
 
   ASSERT_EQ(isolate->builtins()->OsrAfterStackCheck()->entry(),
             Assembler::target_address_at(call_target_address));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64