When constant folding reference variables with an initializer to the

initializer, don't fold paramters. Their initializers are just default
arguments which can be overridden. This fixes some spectacular regressions due
to more things making it into the constant folding.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@103904 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 17 insertions, 0 deletions

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index f903035d22..dc614018ec 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -355,6 +355,10 @@ bool LValueExprEvaluator::VisitDeclRefExpr(DeclRefExpr *E) {
   } else if (VarDecl* VD = dyn_cast<VarDecl>(E->getDecl())) {
     if (!VD->getType()->isReferenceType())
       return Success(E);
+    // Reference parameters can refer to anything even if they have an
+    // "initializer" in the form of a default argument.
+    if (isa<ParmVarDecl>(VD))
+      return false;
     // FIXME: Check whether VD might be overridden!
     if (const Expr *Init = VD->getAnyInitializer())
       return Visit(const_cast<Expr *>(Init));
diff --git a/test/CodeGenCXX/references.cpp b/test/CodeGenCXX/references.cpp
index 5a5947dd81..3ae1e474f8 100644
--- a/test/CodeGenCXX/references.cpp
+++ b/test/CodeGenCXX/references.cpp
@@ -155,3 +155,16 @@ void f0(s1 a) { s1 b = a; }
 // CHECK: load
 // CHECK: ret
 const int &f2() { return 0; }
+
+// Don't constant fold const reference parameters with default arguments to
+// their default arguments.
+namespace N1 {
+  const int foo = 1;
+  // CHECK: @_ZN2N14test
+  int test(const int& arg = foo) {
+    // Ensure this array is on the stack where we can set values instead of
+    // being a global constant.
+    // CHECK: %args_array = alloca
+    const int* const args_array[] = { &arg };
+  }
+}