Fix GCC 5.4 error on ubuntu 16.04

The stock GCC on Ubuntu 16.04 complains these constants
are unused (possibly gcc issue). This CL changes these
to constexpr to workaround gcc errors.

R=clemensh@chromium.org, joransiu@ca.ibm.com

Change-Id: I8c1772e91744bc46ace6bee576b90d40c0cdf41f
Reviewed-on: https://chromium-review.googlesource.com/881554Reviewed-by: Hannes Payer <hpayer@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#50936}

src/handles.cc

@@ -110,7 +110,7 @@ void HandleScope::DeleteExtensions(Isolate* isolate) {
 void HandleScope::ZapRange(Object** start, Object** end) {
   DCHECK_LE(end - start, kHandleBlockSize);
   for (Object** p = start; p != end; p++) {
-    *reinterpret_cast<Address*>(p) = kHandleZapValue;
+    *reinterpret_cast<Address*>(p) = reinterpret_cast<Address>(kHandleZapValue);
   }
 }
 #endif

src/heap/heap.cc

@@ -4945,7 +4945,8 @@ void Heap::ZapFromSpace() {
        PageRange(new_space_->FromSpaceStart(), new_space_->FromSpaceEnd())) {
     for (Address cursor = page->area_start(), limit = page->area_end();
          cursor < limit; cursor += kPointerSize) {
-      Memory::Address_at(cursor) = kFromSpaceZapValue;
+      Memory::Address_at(cursor) =
+          reinterpret_cast<Address>(kFromSpaceZapValue);
     }
   }
 }

src/heap/spaces.cc

@@ -1106,7 +1106,7 @@ bool MemoryAllocator::UncommitBlock(Address start, size_t size) {
 
 void MemoryAllocator::ZapBlock(Address start, size_t size) {
   for (size_t s = 0; s + kPointerSize <= size; s += kPointerSize) {
-    Memory::Address_at(start + s) = kZapValue;
+    Memory::Address_at(start + s) = reinterpret_cast<Address>(kZapValue);
   }
 }
 

src/x64/macro-assembler-x64.cc

@@ -186,7 +186,8 @@ void MacroAssembler::PushAddress(ExternalReference source) {
   int64_t address = reinterpret_cast<int64_t>(source.address());
   if (is_int32(address) && !serializer_enabled()) {
     if (emit_debug_code()) {
-      Move(kScratchRegister, kZapValue, RelocInfo::NONE);
+      Move(kScratchRegister, reinterpret_cast<Address>(kZapValue),
+           RelocInfo::NONE);
     }
     Push(Immediate(static_cast<int32_t>(address)));
     return;
@@ -255,8 +256,8 @@ void MacroAssembler::RecordWriteField(Register object, int offset,
   // Clobber clobbered input registers when running with the debug-code flag
   // turned on to provoke errors.
   if (emit_debug_code()) {
-    Move(value, kZapValue, RelocInfo::NONE);
-    Move(dst, kZapValue, RelocInfo::NONE);
+    Move(value, reinterpret_cast<Address>(kZapValue), RelocInfo::NONE);
+    Move(dst, reinterpret_cast<Address>(kZapValue), RelocInfo::NONE);
   }
 }
 
@@ -386,8 +387,8 @@ void MacroAssembler::RecordWrite(Register object, Register address,
   // Clobber clobbered registers when running with the debug-code flag
   // turned on to provoke errors.
   if (emit_debug_code()) {
-    Move(address, kZapValue, RelocInfo::NONE);
-    Move(value, kZapValue, RelocInfo::NONE);
+    Move(address, reinterpret_cast<Address>(kZapValue), RelocInfo::NONE);
+    Move(value, reinterpret_cast<Address>(kZapValue), RelocInfo::NONE);
   }
 }