diff --git a/compiler-rt/lib/hwasan/hwasan.h b/compiler-rt/lib/hwasan/hwasan.h
--- a/compiler-rt/lib/hwasan/hwasan.h
+++ b/compiler-rt/lib/hwasan/hwasan.h
@@ -37,8 +37,15 @@
 
 // TBI (Top Byte Ignore) feature of AArch64: bits [63:56] are ignored in address
 // translation and can be used to store a tag.
-const unsigned kAddressTagShift = 56;
-const uptr kAddressTagMask = 0xFFUL << kAddressTagShift;
+constexpr unsigned kAddressTagShift = 56;
+constexpr unsigned kTagBits = 8;
+
+// Mask for extracting tag bits from the lower 8 bits.
+constexpr uptr kTagMask = (1UL << kTagBits) - 1;
+
+// Masks for extracting and removing tags from full pointers.
+constexpr uptr kAddressTagMask = 0xFFUL << kAddressTagShift;
+constexpr uptr kAddressUntagMask = ~(kTagMask << kAddressTagShift);
 
 // Minimal alignment of the shadow base address. Determines the space available
 // for threads and stack histories. This is an ABI constant.
@@ -54,7 +61,7 @@
 }
 
 static inline uptr UntagAddr(uptr tagged_addr) {
-  return tagged_addr & ~kAddressTagMask;
+  return tagged_addr & kAddressUntagMask;
 }
 
 static inline void *UntagPtr(const void *tagged_ptr) {
@@ -63,7 +70,7 @@
 }
 
 static inline uptr AddTagToPointer(uptr p, tag_t tag) {
-  return (p & ~kAddressTagMask) | ((uptr)tag << kAddressTagShift);
+  return (p & kAddressUntagMask) | ((uptr)tag << kAddressTagShift);
 }
 
 namespace __hwasan {
diff --git a/compiler-rt/lib/hwasan/hwasan_checks.h b/compiler-rt/lib/hwasan/hwasan_checks.h
--- a/compiler-rt/lib/hwasan/hwasan_checks.h
+++ b/compiler-rt/lib/hwasan/hwasan_checks.h
@@ -81,7 +81,7 @@
 
 template <ErrorAction EA, AccessType AT, unsigned LogSize>
 __attribute__((always_inline, nodebug)) static void CheckAddress(uptr p) {
-  uptr ptr_raw = p & ~kAddressTagMask;
+  uptr ptr_raw = p & kAddressUntagMask;
   tag_t mem_tag = *(tag_t *)MemToShadow(ptr_raw);
   if (UNLIKELY(!PossiblyShortTagMatches(mem_tag, p, 1 << LogSize))) {
     SigTrap<0x20 * (EA == ErrorAction::Recover) +
@@ -97,7 +97,7 @@
   if (sz == 0)
     return;
   tag_t ptr_tag = GetTagFromPointer(p);
-  uptr ptr_raw = p & ~kAddressTagMask;
+  uptr ptr_raw = p & kAddressUntagMask;
   tag_t *shadow_first = (tag_t *)MemToShadow(ptr_raw);
   tag_t *shadow_last = (tag_t *)MemToShadow(ptr_raw + sz);
   for (tag_t *t = shadow_first; t < shadow_last; ++t)
diff --git a/compiler-rt/lib/hwasan/hwasan_thread.cpp b/compiler-rt/lib/hwasan/hwasan_thread.cpp
--- a/compiler-rt/lib/hwasan/hwasan_thread.cpp
+++ b/compiler-rt/lib/hwasan/hwasan_thread.cpp
@@ -121,10 +121,10 @@
       if (!random_buffer_)
         random_buffer_ = random_state_ = xorshift(random_state_);
       CHECK(random_buffer_);
-      tag = random_buffer_ & 0xFF;
-      random_buffer_ >>= 8;
+      tag = random_buffer_ & kTagMask;
+      random_buffer_ >>= kTagBits;
     } else {
-      tag = random_state_ = (random_state_ + 1) & 0xFF;
+      tag = random_state_ = (random_state_ + 1) & kTagMask;
     }
   } while (!tag);
   return tag;