[clang][Interp] Cleaning up FIXMEs added during ArrayInitLoopExpr implementation. (#70053)

This patch removes the two `FIXME`s that were added with patches related
to the expression mentioned in the title.

Author: isuckatcs

clang/lib/AST/Interp/ByteCodeExprGen.cpp

@@ -1056,21 +1056,17 @@ bool ByteCodeExprGen<Emitter>::VisitArrayInitLoopExpr(
     const ArrayInitLoopExpr *E) {
   assert(Initializing);
   assert(!DiscardResult);
+
+  // We visit the common opaque expression here once so we have its value
+  // cached.
+  if (!this->discard(E->getCommonExpr()))
+    return false;
+
   // TODO: This compiles to quite a lot of bytecode if the array is larger.
   //   Investigate compiling this to a loop.
-
   const Expr *SubExpr = E->getSubExpr();
-  const Expr *CommonExpr = E->getCommonExpr();
   size_t Size = E->getArraySize().getZExtValue();
 
-  // If the common expression is an opaque expression, we visit it
-  // here once so we have its value cached.
-  // FIXME: This might be necessary (or useful) for all expressions.
-  if (isa<OpaqueValueExpr>(CommonExpr)) {
-    if (!this->discard(CommonExpr))
-      return false;
-  }
-
   // So, every iteration, we execute an assignment here
   // where the LHS is on the stack (the target array)
   // and the RHS is our SubExpr.
@@ -1107,13 +1103,13 @@ bool ByteCodeExprGen<Emitter>::VisitOpaqueValueExpr(const OpaqueValueExpr *E) {
     return false;
 
   // Here the local variable is created but the value is removed from the stack,
-  // so we put it back, because the caller might need it.
+  // so we put it back if the caller needs it.
   if (!DiscardResult) {
     if (!this->emitGetLocal(SubExprT, *LocalIndex, E))
       return false;
   }
 
-  // FIXME: Ideally the cached value should be cleaned up later.
+  // This is cleaned up when the local variable is destroyed.
   OpaqueExprs.insert({E, *LocalIndex});
 
   return true;

clang/lib/AST/Interp/ByteCodeExprGen.h

@@ -374,6 +374,7 @@ template <class Emitter> class LocalScope : public VariableScope<Emitter> {
     if (!Idx)
       return;
     this->Ctx->emitDestroy(*Idx, SourceInfo{});
+    removeStoredOpaqueValues();
   }
 
   /// Overriden to support explicit destruction.
@@ -382,6 +383,7 @@ template <class Emitter> class LocalScope : public VariableScope<Emitter> {
       return;
     this->emitDestructors();
     this->Ctx->emitDestroy(*Idx, SourceInfo{});
+    removeStoredOpaqueValues();
     this->Idx = std::nullopt;
   }
 
@@ -403,10 +405,29 @@ template <class Emitter> class LocalScope : public VariableScope<Emitter> {
       if (!Local.Desc->isPrimitive() && !Local.Desc->isPrimitiveArray()) {
         this->Ctx->emitGetPtrLocal(Local.Offset, SourceInfo{});
         this->Ctx->emitRecordDestruction(Local.Desc);
+        removeIfStoredOpaqueValue(Local);
       }
     }
   }
 
+  void removeStoredOpaqueValues() {
+    if (!Idx)
+      return;
+
+    for (const Scope::Local &Local : this->Ctx->Descriptors[*Idx]) {
+      removeIfStoredOpaqueValue(Local);
+    }
+  }
+
+  void removeIfStoredOpaqueValue(const Scope::Local &Local) {
+    if (const auto *OVE =
+            llvm::dyn_cast_if_present<OpaqueValueExpr>(Local.Desc->asExpr())) {
+      if (auto It = this->Ctx->OpaqueExprs.find(OVE);
+          It != this->Ctx->OpaqueExprs.end())
+        this->Ctx->OpaqueExprs.erase(It);
+    };
+  }
+
   /// Index of the scope in the chain.
   std::optional<unsigned> Idx;
 };