1 files changed, 14 insertions, 17 deletions

diff --git a/deps/v8/src/common/ptr-compr-inl.h b/deps/v8/src/common/ptr-compr-inl.h
index fd0f97e904..00a79bb291 100644
--- a/deps/v8/src/common/ptr-compr-inl.h
+++ b/deps/v8/src/common/ptr-compr-inl.h
@@ -25,8 +25,12 @@ V8_INLINE Address GetIsolateRoot(TOnHeapAddress on_heap_addr);
 
 template <>
 V8_INLINE Address GetIsolateRoot<Address>(Address on_heap_addr) {
+  // We subtract 1 here in order to let the compiler generate addition of 32-bit
+  // signed constant instead of 64-bit constant (the problem is that 2Gb looks
+  // like a negative 32-bit value). It's correct because we will never use
+  // leftmost address of V8 heap as |on_heap_addr|.
   return RoundDown<kPtrComprIsolateRootAlignment>(on_heap_addr +
-                                                  kPtrComprIsolateRootBias);
+                                                  kPtrComprIsolateRootBias - 1);
 }
 
 template <>
@@ -34,17 +38,10 @@ V8_INLINE Address GetIsolateRoot<Isolate*>(Isolate* isolate) {
   return isolate->isolate_root();
 }
 
-template <>
-V8_INLINE Address GetIsolateRoot<const Isolate*>(const Isolate* isolate) {
-  return isolate->isolate_root();
-}
-
 // Decompresses smi value.
 V8_INLINE Address DecompressTaggedSigned(Tagged_t raw_value) {
-  // Current compression scheme requires |raw_value| to be sign-extended
-  // from int32_t to intptr_t.
-  intptr_t value = static_cast<intptr_t>(static_cast<int32_t>(raw_value));
-  return static_cast<Address>(value);
+  // For runtime code the upper 32-bits of the Smi value do not matter.
+  return static_cast<Address>(raw_value);
 }
 
 // Decompresses weak or strong heap object pointer or forwarding pointer,
@@ -63,18 +60,18 @@ V8_INLINE Address DecompressTaggedPointer(TOnHeapAddress on_heap_addr,
 template <typename TOnHeapAddress>
 V8_INLINE Address DecompressTaggedAny(TOnHeapAddress on_heap_addr,
                                       Tagged_t raw_value) {
-  // Current compression scheme requires |raw_value| to be sign-extended
-  // from int32_t to intptr_t.
-  intptr_t value = static_cast<intptr_t>(static_cast<int32_t>(raw_value));
-  if (kUseBranchlessPtrDecompression) {
+  if (kUseBranchlessPtrDecompressionInRuntime) {
+    // Current compression scheme requires |raw_value| to be sign-extended
+    // from int32_t to intptr_t.
+    intptr_t value = static_cast<intptr_t>(static_cast<int32_t>(raw_value));
     // |root_mask| is 0 if the |value| was a smi or -1 otherwise.
     Address root_mask = static_cast<Address>(-(value & kSmiTagMask));
     Address root_or_zero = root_mask & GetIsolateRoot(on_heap_addr);
     return root_or_zero + static_cast<Address>(value);
   } else {
-    return HAS_SMI_TAG(value)
-               ? static_cast<Address>(value)
-               : (GetIsolateRoot(on_heap_addr) + static_cast<Address>(value));
+    return HAS_SMI_TAG(raw_value)
+               ? DecompressTaggedSigned(raw_value)
+               : DecompressTaggedPointer(on_heap_addr, raw_value);
   }
 }