Add clang::lifetimebound annotation to ArrayRef constructors.

Author: hokein

llvm/include/llvm/ADT/ArrayRef.h

@@ -70,7 +70,7 @@ namespace llvm {
     /*implicit*/ ArrayRef(std::nullopt_t) {}
 
     /// Construct an ArrayRef from a single element.
-    /*implicit*/ ArrayRef(const T &OneElt)
+    /*implicit*/ ArrayRef(const T &OneElt LLVM_LIFETIME_BOUND)
       : Data(&OneElt), Length(1) {}
 
     /// Construct an ArrayRef from a pointer and length.
@@ -103,7 +103,8 @@ namespace llvm {
 
     /// Construct an ArrayRef from a C array.
     template <size_t N>
-    /*implicit*/ constexpr ArrayRef(const T (&Arr)[N]) : Data(Arr), Length(N) {}
+    /*implicit*/ constexpr ArrayRef(const T (&Arr LLVM_LIFETIME_BOUND)[N])
+        : Data(Arr), Length(N) {}
 
     /// Construct an ArrayRef from a std::initializer_list.
 #if LLVM_GNUC_PREREQ(9, 0, 0)

llvm/include/llvm/Support/Compiler.h

@@ -413,6 +413,12 @@
 #define LLVM_GSL_POINTER
 #endif
 
+#if LLVM_HAS_CPP_ATTRIBUTE(clang::lifetimebound)
+#define LLVM_LIFETIME_BOUND [[clang::lifetimebound]]
+#else
+#define LLVM_LLVM_LIFETIME_BOUND
+#endif
+
 #if LLVM_HAS_CPP_ATTRIBUTE(nodiscard) >= 201907L
 #define LLVM_CTOR_NODISCARD [[nodiscard]]
 #else