[clang][bytecode] Overrride locs for certain CXXConstructExprs (llvm#152185)

Do it only if we will end up skipping the initializer anyway because
it's a trivial copy or move constructor.

Author: tbaederr

clang/lib/AST/ByteCode/Compiler.cpp

@@ -5997,6 +5997,23 @@ bool Compiler<Emitter>::checkLiteralType(const Expr *E) {
   return this->emitCheckLiteralType(E->getType().getTypePtr(), E);
 }
 
+static bool initNeedsOverridenLoc(const CXXCtorInitializer *Init) {
+  const Expr *InitExpr = Init->getInit();
+
+  if (!Init->isWritten() && !Init->isInClassMemberInitializer() &&
+      !isa<CXXConstructExpr>(InitExpr))
+    return true;
+
+  if (const auto *CE = dyn_cast<CXXConstructExpr>(InitExpr)) {
+    const CXXConstructorDecl *Ctor = CE->getConstructor();
+    if (Ctor->isDefaulted() && Ctor->isCopyOrMoveConstructor() &&
+        Ctor->isTrivial())
+      return true;
+  }
+
+  return false;
+}
+
 template <class Emitter>
 bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
   assert(!ReturnType);
@@ -6071,10 +6088,7 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
       const Record::Field *F = R->getField(Member);
 
       LocOverrideScope<Emitter> LOS(this, SourceInfo{},
-                                    !Init->isWritten() &&
-                                        !Init->isInClassMemberInitializer() &&
-                                        (!isa<CXXConstructExpr>(InitExpr) ||
-                                         Member->isAnonymousStructOrUnion()));
+                                    initNeedsOverridenLoc(Init));
       if (!emitFieldInitializer(F, F->Offset, InitExpr, IsUnion))
         return false;
     } else if (const Type *Base = Init->getBaseClass()) {
@@ -6104,10 +6118,7 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
         return false;
     } else if (const IndirectFieldDecl *IFD = Init->getIndirectMember()) {
       LocOverrideScope<Emitter> LOS(this, SourceInfo{},
-                                    !Init->isWritten() &&
-                                        !Init->isInClassMemberInitializer() &&
-                                        !isa<CXXConstructExpr>(InitExpr));
-
+                                    initNeedsOverridenLoc(Init));
       assert(IFD->getChainingSize() >= 2);
 
       unsigned NestedFieldOffset = 0;

clang/lib/AST/ByteCode/InterpFrame.cpp

@@ -133,6 +133,11 @@ static bool shouldSkipInBacktrace(const Function *F) {
       MD && MD->getParent()->isAnonymousStructOrUnion())
     return true;
 
+  if (const auto *Ctor = dyn_cast<CXXConstructorDecl>(FD);
+      Ctor && Ctor->isDefaulted() && Ctor->isTrivial() &&
+      Ctor->isCopyOrMoveConstructor() && Ctor->inits().empty())
+    return true;
+
   return false;
 }
 

clang/test/AST/ByteCode/cxx11.cpp

@@ -318,3 +318,15 @@ namespace PR19010 {
   };
   void test() { constexpr Test t; }
 }
+
+namespace ReadMutableInCopyCtor {
+  struct G {
+    struct X {};
+    union U { X a; };
+    mutable U u; // both-note {{declared here}}
+  };
+  constexpr G g1 = {};
+  constexpr G g2 = g1; // both-error {{must be initialized by a constant expression}} \
+                       // both-note {{read of mutable member 'u'}} \
+                       // both-note {{in call to 'G(g1)'}}
+}

clang/test/SemaCXX/constexpr-value-init.cpp

@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 %s -Wno-uninitialized -std=c++17 -fsyntax-only -verify
+// RUN: %clang_cc1 %s -Wno-uninitialized -std=c++17 -fsyntax-only -verify -fexperimental-new-constant-interpreter
 
 struct A {
   constexpr A() : a(b + 1), b(a + 1) {} // expected-note 5{{outside its lifetime}}