Revert "[sanitizer] Remove GetCurrentThread nullness checks from Allocate"

This reverts commit 4411d1e for
breaking Darwin bots:
  AddressSanitizer-Unit :: ./Asan-x86_64-calls-Noinst-Test/10/16
  AddressSanitizer-Unit :: ./Asan-x86_64-calls-Noinst-Test/12/16
  AddressSanitizer-Unit :: ./Asan-x86_64-calls-Noinst-Test/13/16
  AddressSanitizer-Unit :: ./Asan-x86_64-inline-Noinst-Test/10/16
  AddressSanitizer-Unit :: ./Asan-x86_64-inline-Noinst-Test/12/16
  AddressSanitizer-Unit :: ./Asan-x86_64-inline-Noinst-Test/13/16
  AddressSanitizer-Unit :: ./Asan-x86_64h-calls-Noinst-Test/10/16
  AddressSanitizer-Unit :: ./Asan-x86_64h-calls-Noinst-Test/12/16
  AddressSanitizer-Unit :: ./Asan-x86_64h-calls-Noinst-Test/13/16
  AddressSanitizer-Unit :: ./Asan-x86_64h-inline-Noinst-Test/10/16
  AddressSanitizer-Unit :: ./Asan-x86_64h-inline-Noinst-Test/12/16
  AddressSanitizer-Unit :: ./Asan-x86_64h-inline-Noinst-Test/13/16

Author: cachemeifyoucan

compiler-rt/lib/asan/asan_allocator.cpp

@@ -576,8 +576,15 @@ struct Allocator {
     }
 
     AsanThread *t = GetCurrentThread();
-    void *allocated = allocator.Allocate(
-        GetAllocatorCache(&t->malloc_storage()), needed_size, 8);
+    void *allocated;
+    if (t) {
+      AllocatorCache *cache = GetAllocatorCache(&t->malloc_storage());
+      allocated = allocator.Allocate(cache, needed_size, 8);
+    } else {
+      SpinMutexLock l(&fallback_mutex);
+      AllocatorCache *cache = &fallback_allocator_cache;
+      allocated = allocator.Allocate(cache, needed_size, 8);
+    }
     if (UNLIKELY(!allocated)) {
       SetAllocatorOutOfMemory();
       if (AllocatorMayReturnNull())

compiler-rt/lib/msan/msan_allocator.cpp

@@ -199,8 +199,15 @@ static void *MsanAllocate(BufferedStackTrace *stack, uptr size, uptr alignment,
     ReportRssLimitExceeded(stack);
   }
   MsanThread *t = GetCurrentThread();
-  void *allocated = allocator.Allocate(GetAllocatorCache(&t->malloc_storage()),
-                                       size, alignment);
+  void *allocated;
+  if (t) {
+    AllocatorCache *cache = GetAllocatorCache(&t->malloc_storage());
+    allocated = allocator.Allocate(cache, size, alignment);
+  } else {
+    SpinMutexLock l(&fallback_mutex);
+    AllocatorCache *cache = &fallback_allocator_cache;
+    allocated = allocator.Allocate(cache, size, alignment);
+  }
   if (UNLIKELY(!allocated)) {
     SetAllocatorOutOfMemory();
     if (AllocatorMayReturnNull())