Remove several build-time conditionals on deprecated per-thread.

Since this is a rarely used configuration, we can specialize for per-cpu being
available.  Either way, we need to be able to use the per-thread caches if
per-cpu caches are not available, so our fallbacks get exercised that way.

PiperOrigin-RevId: 565112748
Change-Id: Ib7303fde4af31a71a0107ae99de63c6b5ad2309c

tcmalloc/cpu_cache.h

@@ -2301,8 +2301,8 @@ inline bool UsePerCpuCache(State& state) {
   // into tcmalloc.
   //
   // If the per-CPU cache for a thread is not initialized, we push ourselves
-  // onto the slow path (if !defined(TCMALLOC_DEPRECATED_PERTHREAD)) until this
-  // occurs.  See fast_alloc's use of TryRecordAllocationFast.
+  // onto the slow path until this occurs.  See fast_alloc's use of
+  // TryRecordAllocationFast.
   if (ABSL_PREDICT_TRUE(subtle::percpu::IsFast())) {
     ThreadCache::BecomeIdle();
     return true;

tcmalloc/static_vars.h

@@ -167,7 +167,6 @@ class Static final {
         // this can be a common source of bugs.  Suppress this by casting to
         // int first.
 
-#ifndef TCMALLOC_DEPRECATED_PERTHREAD
         // When the per-cpu cache is enabled, and the thread's current cpu
         // variable is initialized we will try to allocate from the per-cpu
         // cache. If something fails, we bail out to the full malloc.
@@ -176,9 +175,6 @@ class Static final {
         // variable is initialized.
         static_cast<int>(CpuCacheActive()) &
         static_cast<int>(subtle::percpu::IsFastNoInit());
-#else
-        !CpuCacheActive();
-#endif
   }
 
   static size_t metadata_bytes() ABSL_EXCLUSIVE_LOCKS_REQUIRED(pageheap_lock);

tcmalloc/tcmalloc.cc

@@ -564,24 +564,11 @@ static inline ABSL_ATTRIBUTE_ALWAYS_INLINE void FreeSmall(void* ptr,
     return;
   }
 
-#ifndef TCMALLOC_DEPRECATED_PERTHREAD
   // The CPU Cache is enabled, so we're able to take the fastpath.
   ASSERT(tc_globals.CpuCacheActive());
   ASSERT(subtle::percpu::IsFastNoInit());
 
   tc_globals.cpu_cache().Deallocate(ptr, size_class);
-#else   // TCMALLOC_DEPRECATED_PERTHREAD
-  ThreadCache* cache = ThreadCache::GetCacheIfPresent();
-
-  // IsOnFastPath does not track whether or not we have an active ThreadCache on
-  // this thread, so we need to check cache for nullptr.
-  if (ABSL_PREDICT_FALSE(cache == nullptr)) {
-    FreeSmallSlow(ptr, size_class);
-    return;
-  }
-
-  cache->Deallocate(ptr, size_class);
-#endif  // TCMALLOC_DEPRECATED_PERTHREAD
 }
 
 // this helper function is used when FreeSmall (defined above) hits
@@ -961,10 +948,7 @@ using tcmalloc::tcmalloc_internal::MallocPolicy;
 using tcmalloc::tcmalloc_internal::Parameters;
 using tcmalloc::tcmalloc_internal::tc_globals;
 using tcmalloc::tcmalloc_internal::UsePerCpuCache;
-
-#ifdef TCMALLOC_DEPRECATED_PERTHREAD
 using tcmalloc::tcmalloc_internal::ThreadCache;
-#endif  // TCMALLOC_DEPRECATED_PERTHREAD
 
 // Slow path implementation.
 // This function is used by `fast_alloc` if the allocation requires page sized
@@ -1020,15 +1004,6 @@ static inline Pointer ABSL_ATTRIBUTE_ALWAYS_INLINE fast_alloc(Policy policy,
     return slow_alloc(policy, size);
   }
 
-  // When using per-thread caches, we have to check for the presence of the
-  // cache for this thread before we try to sample, as slow_alloc will
-  // also try to sample the allocation.
-#ifdef TCMALLOC_DEPRECATED_PERTHREAD
-  ThreadCache* const cache = ThreadCache::GetCacheIfPresent();
-  if (ABSL_PREDICT_FALSE(cache == nullptr)) {
-    return slow_alloc(policy, size);
-  }
-#endif
   // TryRecordAllocationFast() returns true if no extra logic is required, e.g.:
   // - this allocation does not need to be sampled
   // - no new/delete hooks need to be invoked
@@ -1046,14 +1021,8 @@ static inline Pointer ABSL_ATTRIBUTE_ALWAYS_INLINE fast_alloc(Policy policy,
   // - no new/delete hook is installed and required to be called.
   ASSERT(size_class != 0);
   Pointer ret;
-#ifndef TCMALLOC_DEPRECATED_PERTHREAD
   // The CPU cache should be ready.
   ret = tc_globals.cpu_cache().Allocate<Policy>(size_class);
-#else   // !defined(TCMALLOC_DEPRECATED_PERTHREAD)
-  // The ThreadCache should be ready.
-  ASSERT(cache != nullptr);
-  ret = cache->Allocate<Policy>(size_class);
-#endif  // TCMALLOC_DEPRECATED_PERTHREAD
   if (!Policy::can_return_nullptr()) {
     ret = AssumeNotNull(ret);
   }