[sanitizer] Relax the restriction on SizeClassAllocator64::kAllocatorSize

Commit 278ccda says that kAllocatorSize
must be >= (1<<32), but this is not accurate. This static_assert causes 128GiB
kAllocatorSize to be unable to select DefaultSizeClassMap (kRegionSize is
1<<31).

Relax the restriction to be able to satisfy the largest size class. This allows
DefaultSizeClassMap to be usable with 128GiB kAllocatorSize, with
check-{asan,lsan,sanitizer} passing.

Reviewed By: #sanitizers, vitalybuka, kstoimenov

Differential Revision: https://reviews.llvm.org/D153664

Author: MaskRay

compiler-rt/lib/sanitizer_common/sanitizer_allocator_primary64.h

@@ -635,8 +635,8 @@ class SizeClassAllocator64 {
     return kUsingConstantSpaceBeg ? kSpaceBeg : NonConstSpaceBeg;
   }
   uptr SpaceEnd() const { return  SpaceBeg() + kSpaceSize; }
-  // kRegionSize must be >= 2^32.
-  COMPILER_CHECK((kRegionSize) >= (1ULL << (SANITIZER_WORDSIZE / 2)));
+  // kRegionSize should be able to satisfy the largest size class.
+  static_assert(kRegionSize >= SizeClassMap::kMaxSize);
   // kRegionSize must be <= 2^36, see CompactPtrT.
   COMPILER_CHECK((kRegionSize) <= (1ULL << (SANITIZER_WORDSIZE / 2 + 4)));
   // Call mmap for user memory with at least this size.