Optionally use 31-bits SMI value for 64-bit system

test/cctest/test-log-stack-tracer.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 116 matching lines @@
   }
 }
 
 
 Address TraceExtension::GetFP(const v8::FunctionCallbackInfo<v8::Value>& args) {
   // Convert frame pointer from encoding as smis in the arguments to a pointer.
   CHECK_EQ(2, args.Length());  // Ignore second argument on 32-bit platform.
 #if defined(V8_HOST_ARCH_32_BIT)
   Address fp = *reinterpret_cast<Address*>(*args[0]);
 #elif defined(V8_HOST_ARCH_64_BIT)
+#if !V8_USE_31_BITS_SMI_VALUE
   int64_t low_bits = *reinterpret_cast<uint64_t*>(*args[0]) >> 32;
   int64_t high_bits = *reinterpret_cast<uint64_t*>(*args[1]);
+#else
+  // Low 33 bits ([32, 0]), the least two bits are zero.
+  int64_t low_bits = ((*reinterpret_cast<uint64_t*>(*args[0])) & 0xffffffff)
+                     << 1;
+  // High 32 bits ([63, 32]), 32th bit has been set by low_bits.
+  int64_t high_bits = *reinterpret_cast<uint64_t*>(*args[1]) << 32;
+#endif
   Address fp = reinterpret_cast<Address>(high_bits | low_bits);
 #else
 #error Host architecture is neither 32-bit nor 64-bit.
 #endif
   printf("Trace: %p\n", fp);
   return fp;
 }
 
 
 void TraceExtension::Trace(const v8::FunctionCallbackInfo<v8::Value>& args) {
@@ skipping 57 matching lines @@
   CHECK(frame_iterator.frame()->is_construct());
   frame_iterator.Advance();
   i::StackFrame* calling_frame = frame_iterator.frame();
   CHECK(calling_frame->is_java_script());
 
 #if defined(V8_HOST_ARCH_32_BIT)
   int32_t low_bits = reinterpret_cast<int32_t>(calling_frame->fp());
   args.This()->Set(v8_str("low_bits"), v8_num(low_bits >> 1));
 #elif defined(V8_HOST_ARCH_64_BIT)
   uint64_t fp = reinterpret_cast<uint64_t>(calling_frame->fp());
+#if !V8_USE_31_BITS_SMI_VALUE
   int32_t low_bits = static_cast<int32_t>(fp & 0xffffffff);
   int32_t high_bits = static_cast<int32_t>(fp >> 32);
+#else
+  // Middle 31-bits ([32, 2]), the least two bits are always 0 for FP.
+  int32_t low_bits = static_cast<int32_t>((fp >> 2) & 0xffffffff);
+  // High 31-bits ([63, 33]).
+  int32_t high_bits = static_cast<int32_t>(fp >> 33);
+#endif
   args.This()->Set(v8_str("low_bits"), v8_num(low_bits));
   args.This()->Set(v8_str("high_bits"), v8_num(high_bits));
 #else
 #error Host architecture is neither 32-bit nor 64-bit.
 #endif
   args.GetReturnValue().Set(args.This());
 }
 
 
 // Use the API to create a JSFunction object that calls the above C++ function.
@@ skipping 161 matching lines @@
   CcTest::InitializeVM(TRACE_EXTENSION);
   v8::HandleScope scope(CcTest::isolate());
   CHECK_EQ(0, GetJsEntrySp());
   CompileRun("a = 1; b = a + 1;");
   CHECK_EQ(0, GetJsEntrySp());
   CompileRun("js_entry_sp();");
   CHECK_EQ(0, GetJsEntrySp());
   CompileRun("js_entry_sp_level2();");
   CHECK_EQ(0, GetJsEntrySp());
 }