[Runtime] Use platform specific value for JSReceiver::HashMask

This allows us to remove the loop while calculating the hash value and
just use the HashMask as the mask for ComputeIntegerHash. This
previously overflowed on 32-bit systems failing the Smi::IsValid
check.

Bug: v8:6404
Change-Id: I84610a7592fa9d7ce4fa5cef7903bd50b8e8a4df
Reviewed-on: https://chromium-review.googlesource.com/702675Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48319}

src/objects.cc

@@ -6481,13 +6481,8 @@ Smi* JSObject::GetOrCreateIdentityHash(Isolate* isolate) {
     return Smi::cast(hash_obj);
   }
 
-  int masked_hash;
-  // TODO(gsathya): Remove the loop and pass kHashMask directly to
-  // GenerateIdentityHash.
-  do {
-    int hash = isolate->GenerateIdentityHash(Smi::kMaxValue);
-    masked_hash = hash & JSReceiver::kHashMask;
-  } while (masked_hash == PropertyArray::kNoHashSentinel);
+  int masked_hash = isolate->GenerateIdentityHash(JSReceiver::kHashMask);
+  DCHECK_NE(PropertyArray::kNoHashSentinel, masked_hash);
 
   SetIdentityHash(masked_hash);
   return Smi::FromInt(masked_hash);

src/objects.h

@@ -1951,8 +1951,13 @@ class PropertyArray : public HeapObject {
   typedef BodyDescriptor BodyDescriptorWeak;
 
   static const int kLengthMask = 0x3ff;
+#if V8_TARGET_ARCH_64_BIT
   static const int kHashMask = 0x7ffffc00;
   STATIC_ASSERT(kLengthMask + kHashMask == 0x7fffffff);
+#else
+  static const int kHashMask = 0x3ffffc00;
+  STATIC_ASSERT(kLengthMask + kHashMask == 0x3fffffff);
+#endif
 
   static const int kMaxLength = kLengthMask;
   STATIC_ASSERT(kMaxLength > kMaxNumberOfDescriptors);