[compiler-rt] [scudo] Add EnableMultiRegions mode (PR #98076)

[via llvm-commits]

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@@ -555,18 +715,208 @@ template <typename Config> class SizeClassAllocator64 {
     bool isPopulatingFreeList GUARDED_BY(FLLock) = false;
   };
   struct RegionInfo : UnpaddedRegionInfo {
+    // This is only used when `Config::getEnableMultiRegions` is enabled and is
+    // guarded by the mutex in `RegionInfoManager`.
+    RegionInfo *Next = nullptr;
     char Padding[SCUDO_CACHE_LINE_SIZE -
-                 (sizeof(UnpaddedRegionInfo) % SCUDO_CACHE_LINE_SIZE)] = {};
+                 ((sizeof(UnpaddedRegionInfo) + sizeof(RegionInfo *)) %
+                  SCUDO_CACHE_LINE_SIZE)] = {};
   };
   static_assert(sizeof(RegionInfo) % SCUDO_CACHE_LINE_SIZE == 0, "");
 
-  RegionInfo *getRegionInfo(uptr ClassId) {
-    DCHECK_LT(ClassId, NumClasses);
-    return &RegionInfoArray[ClassId];
-  }
+  template <bool IsMultiRegions = false> struct RegionInfoAlloc {
+    RegionInfo *allocate() {
+      UNREACHABLE("RegionInfo is statically allocated");
+    }
 
-  uptr getRegionBaseByClassId(uptr ClassId) {
-    RegionInfo *Region = getRegionInfo(ClassId);
+    void verifyTheNumberOfAllocatedRegionInfo(uptr NumRegionInfo) {
+      DCHECK_EQ(NumRegionInfo, NumClasses);
+    }
+  };
+
+  template <> struct RegionInfoAlloc</*isMultiRegions=*/true> {
+    RegionInfo *allocate() {
+      ScopedLock L(M);
+      return S.pop();
+    }
+
+    void verifyTheNumberOfAllocatedRegionInfo(uptr NumRegionInfo) {
+      ScopedLock L(M);
+      DCHECK_EQ(NumRegionInfo, S.Size);
+    }
+
+    HybridMutex M;
+    // According to the following,
+    //   DR1351: If the brace-or-equal-initializer of a non-static data
+    //   member invokes a defaulted default constructor of its class or of an
+    //   enclosing class in a potentially evaluated subexpression, the program
+    //   is ill-formed.
+    // So we have to `outline` the `Size`/`Array` into another struct `Storage`.
+    struct Storage {
+      RegionInfo *pop() {
+        if (Size == NumEntries)
+          return nullptr;
+        return &Array[Size++];
+      }
+      // The amount memory used by this allocator is about (NumEntries *
----------------
ChiaHungDuan wrote:

Done

https://github.com/llvm/llvm-project/pull/98076