[x64] Do not compact constants with attached reloc info.

test/cctest/test-assembler-x64.cc

 // Copyright 2009 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 155 matching lines @@
 
   CodeDesc desc;
   assm.GetCode(&desc);
   // Call the function from C++.
   int result =  FUNCTION_CAST<F2>(buffer)(0x1002, 0x2002);
   CHECK_EQ(1, result);
   result =  FUNCTION_CAST<F2>(buffer)(0x1002, 0x2003);
   CHECK_EQ(0, result);
 }
 
+TEST(Regression684407) {
+  CcTest::InitializeVM();
+  // Allocate an executable page of memory.
+  size_t actual_size;
+  byte* buffer = static_cast<byte*>(v8::base::OS::Allocate(
+      Assembler::kMinimalBufferSize, &actual_size, true));
+  CHECK(buffer);
+  Assembler assm(CcTest::i_isolate(), buffer, static_cast<int>(actual_size));
+  Address before = assm.pc();
+  __ cmpl(Operand(arg1, 0),
+          Immediate(0, RelocInfo::WASM_MEMORY_SIZE_REFERENCE));
+  Address after = assm.pc();
+  size_t instruction_size = static_cast<size_t>(after - before);
+  // Check that the immediate is not encoded as uint8.
+  CHECK_LT(sizeof(uint32_t), instruction_size);
+}
 
 TEST(AssemblerX64ImulOperation) {
   CcTest::InitializeVM();
   // Allocate an executable page of memory.
   size_t actual_size;
   byte* buffer = static_cast<byte*>(v8::base::OS::Allocate(
       Assembler::kMinimalBufferSize, &actual_size, true));
   CHECK(buffer);
   Assembler assm(CcTest::i_isolate(), buffer, static_cast<int>(actual_size));
 
@@ skipping 2327 matching lines @@
 #ifdef OBJECT_PRINT
   OFStream os(stdout);
   code->Print(os);
 #endif
 
   F9 f = FUNCTION_CAST<F9>(code->entry());
   CHECK_EQ(-1.5, f(1.5, -1.5));
 }
 
 #undef __