[compiler-rt] [asan] Add experimental 'track_poison' flag (PR #133175)

[Thurston Dang via llvm-commits]

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@@ -119,7 +181,7 @@ void __asan_poison_memory_region(void const volatile *addr, uptr size) {
       if (beg.offset > 0) {
         *beg.chunk = Min(value, beg.offset);
       } else {
-        *beg.chunk = kAsanUserPoisonedMemoryMagic;
+        *beg.chunk = poison_magic;
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thurstond wrote:

Multiple poison values let us shard into different ring buffers. Having multiple ring buffers:

- reduces the likelihood of lost records (race conditions) when pushing onto the ring buffers
- improves the lookup speed when searching for the stack, because we can look up in one of the smaller ring buffers instead of one giant ring buffer

https://github.com/llvm/llvm-project/pull/133175