[compiler-rt] [NFC] Make RingBuffer an atomic pointer (PR #82547)

[via llvm-commits]

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@@ -1061,16 +1064,29 @@ class Allocator {
       atomic_u32 DeallocationTrace;
       atomic_u32 DeallocationTid;
     };
-
+    StackDepot *Depot = nullptr;
+    uptr StackDepotSize = 0;
+    MemMapT RawRingBufferMap;
+    MemMapT RawStackDepotMap;
+    u32 RingBufferElements;
     atomic_uptr Pos;
     // An array of Size (at least one) elements of type Entry is immediately
     // following to this struct.
   };
   // Pointer to memory mapped area starting with AllocationRingBuffer struct,
   // and immediately followed by Size elements of type Entry.
-  char *RawRingBuffer = {};
-  u32 RingBufferElements = 0;
-  MemMapT RawRingBufferMap;
+  atomic_voidptr RingBuffer = {};
+
+  AllocationRingBuffer *getRingBuffer() {
+    return reinterpret_cast<AllocationRingBuffer *>(
+        atomic_load(&RingBuffer, memory_order_acquire));
+  }
+
+  AllocationRingBuffer *getRingBufferIfEnabled(const Options &Options) {
+    if (!UNLIKELY(Options.get(OptionBit::TrackAllocationStacks)))
+      return nullptr;
+    return getRingBuffer();
+  }
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ChiaHungDuan wrote:

The difference between this two functions is unclear to me because both call sites need to check the nullity. I think the better to do this is to inline this function. I.e., check the `TrackAllocationStacks` in the caller

https://github.com/llvm/llvm-project/pull/82547