[clang][bytecode] Use in Expr::tryEvaluateStrLen() (#149677)

Fixes #138475

2 files changed, 41 insertions, 0 deletions

diff --git a/clang/lib/AST/ByteCode/Context.cpp b/clang/lib/AST/ByteCode/Context.cpp
index ead6e4a..9e683d7 100644
--- a/clang/lib/AST/ByteCode/Context.cpp
+++ b/clang/lib/AST/ByteCode/Context.cpp
@@ -235,6 +235,43 @@ bool Context::evaluateCharRange(State &Parent, const Expr *SizeExpr,
   return evaluateStringRepr(Parent, SizeExpr, PtrExpr, Result);
 }
 
+bool Context::evaluateStrlen(State &Parent, const Expr *E, uint64_t &Result) {
+  assert(Stk.empty());
+  Compiler<EvalEmitter> C(*this, *P, Parent, Stk);
+
+  auto PtrRes = C.interpretAsPointer(E, [&](const Pointer &Ptr) {
+    const Descriptor *FieldDesc = Ptr.getFieldDesc();
+    if (!FieldDesc->isPrimitiveArray())
+      return false;
+
+    unsigned N = Ptr.getNumElems();
+    if (Ptr.elemSize() == 1) {
+      Result = strnlen(reinterpret_cast<const char *>(Ptr.getRawAddress()), N);
+      return Result != N;
+    }
+
+    PrimType ElemT = FieldDesc->getPrimType();
+    Result = 0;
+    for (unsigned I = Ptr.getIndex(); I != N; ++I) {
+      INT_TYPE_SWITCH(ElemT, {
+        auto Elem = Ptr.atIndex(I).deref<T>();
+        if (Elem.isZero())
+          return true;
+        ++Result;
+      });
+    }
+    // We didn't find a 0 byte.
+    return false;
+  });
+
+  if (PtrRes.isInvalid()) {
+    C.cleanup();
+    Stk.clear();
+    return false;
+  }
+  return true;
+}
+
 const LangOptions &Context::getLangOpts() const { return Ctx.getLangOpts(); }
 
 static PrimType integralTypeToPrimTypeS(unsigned BitWidth) {
diff --git a/clang/lib/AST/ByteCode/Context.h b/clang/lib/AST/ByteCode/Context.h
index acf7504..6065d3e 100644
--- a/clang/lib/AST/ByteCode/Context.h
+++ b/clang/lib/AST/ByteCode/Context.h
@@ -66,6 +66,10 @@ public:
   bool evaluateCharRange(State &Parent, const Expr *SizeExpr,
                          const Expr *PtrExpr, std::string &Result);
 
+  /// Evalute \param E and if it can be evaluated to a string literal,
+  /// run strlen() on it.
+  bool evaluateStrlen(State &Parent, const Expr *E, uint64_t &Result);
+
   /// Returns the AST context.
   ASTContext &getASTContext() const { return Ctx; }
   /// Returns the language options.