[clang] Introduce intra-procedural lifetime analysis in Clang (PR #142313)

[Yitzhak Mandelbaum via cfe-commits]

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@@ -0,0 +1,728 @@
+#include "clang/Analysis/Analyses/LifetimeSafety.h"
+#include "clang/AST/Decl.h"
+#include "clang/AST/Expr.h"
+#include "clang/AST/StmtVisitor.h"
+#include "clang/AST/Type.h"
+#include "clang/Analysis/AnalysisDeclContext.h"
+#include "clang/Analysis/CFG.h"
+#include "clang/Analysis/FlowSensitive/DataflowWorklist.h"
+#include "llvm/ADT/ImmutableMap.h"
+#include "llvm/ADT/ImmutableSet.h"
+#include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/TimeProfiler.h"
+#include <vector>
+
+namespace clang {
+namespace {
+
+struct Point {
+  const clang::CFGBlock *Block;
+  /// Index into Block->Elements().
+  unsigned ElementIndex;
+
+  Point(const clang::CFGBlock *B = nullptr, unsigned Idx = 0)
+      : Block(B), ElementIndex(Idx) {}
+
+  bool operator==(const Point &Other) const {
+    return Block == Other.Block && ElementIndex == Other.ElementIndex;
+  }
+};
+
+/// Represents the storage location being borrowed, e.g., a specific stack
+/// variable.
+/// TODO: Handle member accesseslike `s.y`.
+struct Path {
+  const clang::ValueDecl *D;
+
+  enum class Kind : uint8_t {
+    StackVariable,
+    Heap,            // TODO: Handle.
+    Field,           // TODO: Handle.
+    ArrayElement,    // TODO: Handle.
+    TemporaryObject, // TODO: Handle.
+    StaticOrGlobal,  // TODO: Handle.
+  };
+
+  Kind PathKind;
+
+  Path(const clang::ValueDecl *D, Kind K) : D(D), PathKind(K) {}
+};
+
+using LoanID = uint32_t;
+using OriginID = uint32_t;
+
+/// Information about a single borrow, or "Loan". A loan is created when a
+/// reference or pointer is taken.
+struct LoanInfo {
+  /// TODO: Represent opaque loans.
+  /// TODO: Represent nullptr: loans to no path. Accessing it UB! Currently it
+  /// is represented as empty LoanSet
+  LoanID ID;
+  Path SourcePath;
+  SourceLocation IssueLoc;
+
+  LoanInfo(LoanID id, Path path, SourceLocation loc)
+      : ID(id), SourcePath(path), IssueLoc(loc) {}
+};
+
+enum class OriginKind : uint8_t { Variable, ExpressionResult };
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ymand wrote:

Since a variable (reference) is an expression, this is bit surprising. Is the `Variable` case referring to the variable _declaration_? If so, maybe make that expression (like Declaration vs Expression instead)?

https://github.com/llvm/llvm-project/pull/142313