[PATCH] D147840: [clang][Interp] Handle DiscardResult for DeclRef- and ParenExprs

[Timm Bäder via Phabricator via cfe-commits]

tbaeder created this revision.
tbaeder added reviewers: aaron.ballman, tahonermann, shafik, erichkeane.
Herald added a project: All.
tbaeder requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

  Fixes https://github.com/llvm/llvm-project/issues/62004


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D147840

Files:
  clang/lib/AST/Interp/ByteCodeExprGen.cpp
  clang/test/AST/Interp/literals.cpp


Index: clang/test/AST/Interp/literals.cpp
===================================================================
--- clang/test/AST/Interp/literals.cpp
+++ clang/test/AST/Interp/literals.cpp
@@ -780,4 +780,18 @@
   return F{12}.a;
 }
 static_assert(ignoredDecls() == 12, "");
+
+struct A{};
+constexpr int ignoredExprs() {
+  (void)(1 / 2);
+  A a;
+  a; // expected-warning {{unused}} \
+     // ref-warning {{unused}}
+  (void)a;
+  (a); // expected-warning {{unused}} \
+       // ref-warning {{unused}}
+
+  return 0;
+}
+
 #endif
Index: clang/lib/AST/Interp/ByteCodeExprGen.cpp
===================================================================
--- clang/lib/AST/Interp/ByteCodeExprGen.cpp
+++ clang/lib/AST/Interp/ByteCodeExprGen.cpp
@@ -231,7 +231,15 @@
 
 template <class Emitter>
 bool ByteCodeExprGen<Emitter>::VisitParenExpr(const ParenExpr *PE) {
-  return this->visit(PE->getSubExpr());
+  if (!this->visit(PE->getSubExpr()))
+    return false;
+
+  if (DiscardResult) {
+    std::optional<PrimType> T = classify(PE->getSubExpr()).value_or(PT_Ptr);
+    return this->emitPop(*T, PE);
+  }
+
+  return true;
 }
 
 template <class Emitter>
@@ -2058,6 +2066,9 @@
 
 template <class Emitter>
 bool ByteCodeExprGen<Emitter>::VisitDeclRefExpr(const DeclRefExpr *E) {
+  if (DiscardResult)
+    return true;
+
   const auto *D = E->getDecl();
 
   if (const auto *ECD = dyn_cast<EnumConstantDecl>(D)) {


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