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

test/cctest/test-log-stack-tracer.cc

Index: test/cctest/test-log-stack-tracer.cc
diff --git a/test/cctest/test-log-stack-tracer.cc b/test/cctest/test-log-stack-tracer.cc
index 7c3567c140bf2bb4da366f79f3c61e5dca0a3f61..04509987e663c8bbd00128cbff21fe155d071673 100644
--- a/test/cctest/test-log-stack-tracer.cc
+++ b/test/cctest/test-log-stack-tracer.cc
@@ -134,8 +134,16 @@ Address TraceExtension::GetFP(const v8::FunctionCallbackInfo<v8::Value>& args) {
 #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.
@@ -213,8 +221,15 @@ static void construct_call(const v8::FunctionCallbackInfo<v8::Value>& args) {
   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