Add utility to evaluate lvalues which are an offset relative to a stack

location.  Patch by Enea Zaffanella.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@81672 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/AST/Expr.h

@@ -248,9 +248,14 @@ class Expr : public Stmt {
   /// must be called on an expression that constant folds to an integer.
   llvm::APSInt EvaluateAsInt(ASTContext &Ctx) const;
 
-  /// EvaluateAsLValue - Evaluate an expression to see if it's a valid LValue.
+  /// EvaluateAsLValue - Evaluate an expression to see if it's a lvalue
+  /// with link time known address.
   bool EvaluateAsLValue(EvalResult &Result, ASTContext &Ctx) const;
 
+  /// EvaluateAsAnyLValue - The same as EvaluateAsLValue, except that it
+  /// also succeeds on stack based, immutable address lvalues.
+  bool EvaluateAsAnyLValue(EvalResult &Result, ASTContext &Ctx) const;
+
   /// isNullPointerConstant - C99 6.3.2.3p3 -  Return true if this is either an
   /// integer constant expression with the value zero, or if this is one that is
   /// cast to void*.

lib/AST/ExprConstant.cpp

@@ -46,8 +46,12 @@ struct EvalInfo {
   /// EvalResult - Contains information about the evaluation.
   Expr::EvalResult &EvalResult;
 
-  EvalInfo(ASTContext &ctx, Expr::EvalResult& evalresult) : Ctx(ctx),
-           EvalResult(evalresult) {}
+  /// AnyLValue - Stack based LValue results are not discarded.
+  bool AnyLValue;
+
+  EvalInfo(ASTContext &ctx, Expr::EvalResult& evalresult,
+           bool anylvalue = false)
+    : Ctx(ctx), EvalResult(evalresult), AnyLValue(anylvalue) {}
 };
 
 
@@ -189,7 +193,7 @@ APValue LValueExprEvaluator::VisitDeclRefExpr(DeclRefExpr *E) {
   if (isa<FunctionDecl>(E->getDecl())) {
     return APValue(E, 0);
   } else if (VarDecl* VD = dyn_cast<VarDecl>(E->getDecl())) {
-    if (!VD->hasGlobalStorage())
+    if (!Info.AnyLValue && !VD->hasGlobalStorage())
       return APValue();
     if (!VD->getType()->isReferenceType())
       return APValue(E, 0);
@@ -209,9 +213,9 @@ APValue LValueExprEvaluator::VisitBlockExpr(BlockExpr *E) {
 }
 
 APValue LValueExprEvaluator::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
-  if (E->isFileScope())
-    return APValue(E, 0);
-  return APValue();
+  if (!Info.AnyLValue && !E->isFileScope())
+    return APValue();
+  return APValue(E, 0);
 }
 
 APValue LValueExprEvaluator::VisitMemberExpr(MemberExpr *E) {
@@ -1786,6 +1790,12 @@ bool Expr::EvaluateAsLValue(EvalResult &Result, ASTContext &Ctx) const {
   return EvaluateLValue(this, Result.Val, Info) && !Result.HasSideEffects;
 }
 
+bool Expr::EvaluateAsAnyLValue(EvalResult &Result, ASTContext &Ctx) const {
+  EvalInfo Info(Ctx, Result, true);
+
+  return EvaluateLValue(this, Result.Val, Info) && !Result.HasSideEffects;
+}
+
 /// isEvaluatable - Call Evaluate to see if this expression can be constant
 /// folded, but discard the result.
 bool Expr::isEvaluatable(ASTContext &Ctx) const {