[PATCH] D46961: [scudo] Quarantine optimization

[Kostya Kortchinsky via Phabricator via llvm-commits]

cryptoad created this revision.
cryptoad added a reviewer: alekseyshl.
Herald added subscribers: Sanitizers, delcypher.

It turns out that the previous code construct was not optimizing the allocation
and deallocation of batches. The class id was read as a class member (even
though a precomputed one) and nothing else was optimized. By changing the
construct this way, the compiler actually optimizes most of the allocation and
deallocation away to only work with a single class id, which not only saves some
CPU but also some code footprint.


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D46961

Files:
  lib/scudo/scudo_allocator.cpp


Index: lib/scudo/scudo_allocator.cpp
===================================================================
--- lib/scudo/scudo_allocator.cpp
+++ lib/scudo/scudo_allocator.cpp
@@ -197,16 +197,17 @@
   // that the batches are indeed serviced by the Primary.
   // TODO(kostyak): figure out the best way to protect the batches.
   void *Allocate(uptr Size) {
+    const uptr BatchClassId = SizeClassMap::ClassID(sizeof(QuarantineBatch));
     return getBackendAllocator().allocatePrimary(Cache_, BatchClassId);
   }
 
   void Deallocate(void *Ptr) {
+    const uptr BatchClassId = SizeClassMap::ClassID(sizeof(QuarantineBatch));
     getBackendAllocator().deallocatePrimary(Cache_, Ptr, BatchClassId);
   }
 
   AllocatorCache *Cache_;
   COMPILER_CHECK(sizeof(QuarantineBatch) < SizeClassMap::kMaxSize);
-  const uptr BatchClassId = SizeClassMap::ClassID(sizeof(QuarantineBatch));
 };
 
 typedef Quarantine<QuarantineCallback, void> ScudoQuarantine;


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