[clang][bytecode] Make union activation more granular (#148835)

Only activate things if the syntactical structure suggests so. This adds
a bunch of new opcodes to control whether to activate in stores, etc.

Fixes #134789

1 files changed, 141 insertions, 49 deletions

diff --git a/clang/lib/AST/ByteCode/Compiler.cpp b/clang/lib/AST/ByteCode/Compiler.cpp
index afa3b7e..ea473730 100644
--- a/clang/lib/AST/ByteCode/Compiler.cpp
+++ b/clang/lib/AST/ByteCode/Compiler.cpp
@@ -25,6 +25,34 @@ using APSInt = llvm::APSInt;
 namespace clang {
 namespace interp {
 
+static bool refersToUnion(const Expr *E) {
+  for (;;) {
+    if (const auto *ME = dyn_cast<MemberExpr>(E)) {
+      if (const auto *FD = dyn_cast<FieldDecl>(ME->getMemberDecl());
+          FD && FD->getParent()->isUnion())
+        return true;
+      E = ME->getBase();
+      continue;
+    }
+
+    if (const auto *ASE = dyn_cast<ArraySubscriptExpr>(E)) {
+      E = ASE->getBase()->IgnoreImplicit();
+      continue;
+    }
+
+    if (const auto *ICE = dyn_cast<ImplicitCastExpr>(E);
+        ICE && (ICE->getCastKind() == CK_NoOp ||
+                ICE->getCastKind() == CK_DerivedToBase ||
+                ICE->getCastKind() == CK_UncheckedDerivedToBase)) {
+      E = ICE->getSubExpr();
+      continue;
+    }
+
+    break;
+  }
+  return false;
+}
+
 static std::optional<bool> getBoolValue(const Expr *E) {
   if (const auto *CE = dyn_cast_if_present<ConstantExpr>(E);
       CE && CE->hasAPValueResult() &&
@@ -880,22 +908,11 @@ bool Compiler<Emitter>::VisitBinaryOperator(const BinaryOperator *BO) {
       return this->VisitPointerArithBinOp(BO);
   }
 
-  // Assignments require us to evalute the RHS first.
-  if (BO->getOpcode() == BO_Assign) {
-
-    if (!visit(RHS) || !visit(LHS))
-      return false;
-
-    // We don't support assignments in C.
-    if (!Ctx.getLangOpts().CPlusPlus && !this->emitInvalid(BO))
-      return false;
+  if (BO->getOpcode() == BO_Assign)
+    return this->visitAssignment(LHS, RHS, BO);
 
-    if (!this->emitFlip(*LT, *RT, BO))
-      return false;
-  } else {
-    if (!visit(LHS) || !visit(RHS))
-      return false;
-  }
+  if (!visit(LHS) || !visit(RHS))
+    return false;
 
   // For languages such as C, cast the result of one
   // of our comparision opcodes to T (which is usually int).
@@ -946,22 +963,6 @@ bool Compiler<Emitter>::VisitBinaryOperator(const BinaryOperator *BO) {
     if (BO->getType()->isFloatingType())
       return Discard(this->emitDivf(getFPOptions(BO), BO));
     return Discard(this->emitDiv(*T, BO));
-  case BO_Assign:
-    if (DiscardResult)
-      return LHS->refersToBitField() ? this->emitStoreBitFieldPop(*T, BO)
-                                     : this->emitStorePop(*T, BO);
-    if (LHS->refersToBitField()) {
-      if (!this->emitStoreBitField(*T, BO))
-        return false;
-    } else {
-      if (!this->emitStore(*T, BO))
-        return false;
-    }
-    // Assignments aren't necessarily lvalues in C.
-    // Load from them in that case.
-    if (!BO->isLValue())
-      return this->emitLoadPop(*T, BO);
-    return true;
   case BO_And:
     return Discard(this->emitBitAnd(*T, BO));
   case BO_Or:
@@ -1790,19 +1791,26 @@ bool Compiler<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
       return this->delegate(Inits[0]);
 
     auto initPrimitiveField = [=](const Record::Field *FieldToInit,
-                                  const Expr *Init, PrimType T) -> bool {
+                                  const Expr *Init, PrimType T,
+                                  bool Activate = false) -> bool {
       InitStackScope<Emitter> ISS(this, isa<CXXDefaultInitExpr>(Init));
       InitLinkScope<Emitter> ILS(this, InitLink::Field(FieldToInit->Offset));
       if (!this->visit(Init))
         return false;
 
-      if (FieldToInit->isBitField())
+      bool BitField = FieldToInit->isBitField();
+      if (BitField && Activate)
+        return this->emitInitBitFieldActivate(T, FieldToInit, E);
+      if (BitField)
         return this->emitInitBitField(T, FieldToInit, E);
+      if (Activate)
+        return this->emitInitFieldActivate(T, FieldToInit->Offset, E);
       return this->emitInitField(T, FieldToInit->Offset, E);
     };
 
     auto initCompositeField = [=](const Record::Field *FieldToInit,
-                                  const Expr *Init) -> bool {
+                                  const Expr *Init,
+                                  bool Activate = false) -> bool {
       InitStackScope<Emitter> ISS(this, isa<CXXDefaultInitExpr>(Init));
       InitLinkScope<Emitter> ILS(this, InitLink::Field(FieldToInit->Offset));
 
@@ -1810,6 +1818,10 @@ bool Compiler<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
       // on the stack and recurse into visitInitializer().
       if (!this->emitGetPtrField(FieldToInit->Offset, Init))
         return false;
+
+      if (Activate && !this->emitActivate(E))
+        return false;
+
       if (!this->visitInitializer(Init))
         return false;
       return this->emitPopPtr(E);
@@ -1829,10 +1841,10 @@ bool Compiler<Emitter>::visitInitList(ArrayRef<const Expr *> Inits,
 
         const Record::Field *FieldToInit = R->getField(FToInit);
         if (std::optional<PrimType> T = classify(Init)) {
-          if (!initPrimitiveField(FieldToInit, Init, *T))
+          if (!initPrimitiveField(FieldToInit, Init, *T, /*Activate=*/true))
             return false;
         } else {
-          if (!initCompositeField(FieldToInit, Init))
+          if (!initCompositeField(FieldToInit, Init, /*Activate=*/true))
             return false;
         }
       }
@@ -2023,7 +2035,8 @@ bool Compiler<Emitter>::visitArrayElemInit(unsigned ElemIndex, const Expr *Init,
 
 template <class Emitter>
 bool Compiler<Emitter>::visitCallArgs(ArrayRef<const Expr *> Args,
-                                      const FunctionDecl *FuncDecl) {
+                                      const FunctionDecl *FuncDecl,
+                                      bool Activate) {
   assert(VarScope->getKind() == ScopeKind::Call);
   llvm::BitVector NonNullArgs = collectNonNullArgs(FuncDecl, Args);
 
@@ -2046,6 +2059,11 @@ bool Compiler<Emitter>::visitCallArgs(ArrayRef<const Expr *> Args,
         return false;
     }
 
+    if (ArgIndex == 1 && Activate) {
+      if (!this->emitActivate(Arg))
+        return false;
+    }
+
     if (FuncDecl && NonNullArgs[ArgIndex]) {
       PrimType ArgT = classify(Arg).value_or(PT_Ptr);
       if (ArgT == PT_Ptr) {
@@ -4227,10 +4245,13 @@ bool Compiler<Emitter>::visitZeroRecordInitializer(const Record *R,
       PrimType T = classifyPrim(D->getType());
       if (!this->visitZeroInitializer(T, QT, E))
         return false;
+      if (R->isUnion()) {
+        if (!this->emitInitFieldActivate(T, Field.Offset, E))
+          return false;
+        break;
+      }
       if (!this->emitInitField(T, Field.Offset, E))
         return false;
-      if (R->isUnion())
-        break;
       continue;
     }
 
@@ -4256,13 +4277,15 @@ bool Compiler<Emitter>::visitZeroRecordInitializer(const Record *R,
     } else
       return false;
 
-    if (!this->emitFinishInitPop(E))
-      return false;
-
     // C++11 [dcl.init]p5: If T is a (possibly cv-qualified) union type, the
     // object's first non-static named data member is zero-initialized
-    if (R->isUnion())
+    if (R->isUnion()) {
+      if (!this->emitFinishInitActivatePop(E))
+        return false;
       break;
+    }
+    if (!this->emitFinishInitPop(E))
+      return false;
   }
 
   for (const Record::Base &B : R->bases()) {
@@ -4326,6 +4349,59 @@ bool Compiler<Emitter>::visitZeroArrayInitializer(QualType T, const Expr *E) {
 }
 
 template <class Emitter>
+bool Compiler<Emitter>::visitAssignment(const Expr *LHS, const Expr *RHS,
+                                        const Expr *E) {
+  if (!classify(E->getType()))
+    return false;
+
+  if (!this->visit(RHS))
+    return false;
+  if (!this->visit(LHS))
+    return false;
+
+  // We don't support assignments in C.
+  if (!Ctx.getLangOpts().CPlusPlus && !this->emitInvalid(E))
+    return false;
+
+  PrimType RHT = classifyPrim(RHS);
+  bool Activates = refersToUnion(LHS);
+  bool BitField = LHS->refersToBitField();
+
+  if (!this->emitFlip(PT_Ptr, RHT, E))
+    return false;
+
+  if (DiscardResult) {
+    if (BitField && Activates)
+      return this->emitStoreBitFieldActivatePop(RHT, E);
+    if (BitField)
+      return this->emitStoreBitFieldPop(RHT, E);
+    if (Activates)
+      return this->emitStoreActivatePop(RHT, E);
+    // Otherwise, regular non-activating store.
+    return this->emitStorePop(RHT, E);
+  }
+
+  auto maybeLoad = [&](bool Result) -> bool {
+    if (!Result)
+      return false;
+    // Assignments aren't necessarily lvalues in C.
+    // Load from them in that case.
+    if (!E->isLValue())
+      return this->emitLoadPop(RHT, E);
+    return true;
+  };
+
+  if (BitField && Activates)
+    return maybeLoad(this->emitStoreBitFieldActivate(RHT, E));
+  if (BitField)
+    return maybeLoad(this->emitStoreBitField(RHT, E));
+  if (Activates)
+    return maybeLoad(this->emitStoreActivate(RHT, E));
+  // Otherwise, regular non-activating store.
+  return maybeLoad(this->emitStore(RHT, E));
+}
+
+template <class Emitter>
 template <typename T>
 bool Compiler<Emitter>::emitConst(T Value, PrimType Ty, const Expr *E) {
   switch (Ty) {
@@ -5067,7 +5143,7 @@ bool Compiler<Emitter>::VisitCallExpr(const CallExpr *E) {
       return false;
   }
 
-  if (!this->visitCallArgs(Args, FuncDecl))
+  if (!this->visitCallArgs(Args, FuncDecl, IsAssignmentOperatorCall))
     return false;
 
   // Undo the argument reversal we did earlier.
@@ -5851,7 +5927,8 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
   assert(!ReturnType);
 
   auto emitFieldInitializer = [&](const Record::Field *F, unsigned FieldOffset,
-                                  const Expr *InitExpr) -> bool {
+                                  const Expr *InitExpr,
+                                  bool Activate = false) -> bool {
     // We don't know what to do with these, so just return false.
     if (InitExpr->getType().isNull())
       return false;
@@ -5860,8 +5937,13 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
       if (!this->visit(InitExpr))
         return false;
 
-      if (F->isBitField())
+      bool BitField = F->isBitField();
+      if (BitField && Activate)
+        return this->emitInitThisBitFieldActivate(*T, F, FieldOffset, InitExpr);
+      if (BitField)
         return this->emitInitThisBitField(*T, F, FieldOffset, InitExpr);
+      if (Activate)
+        return this->emitInitThisFieldActivate(*T, FieldOffset, InitExpr);
       return this->emitInitThisField(*T, FieldOffset, InitExpr);
     }
     // Non-primitive case. Get a pointer to the field-to-initialize
@@ -5870,6 +5952,9 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
     if (!this->emitGetPtrThisField(FieldOffset, InitExpr))
       return false;
 
+    if (Activate && !this->emitActivate(InitExpr))
+      return false;
+
     if (!this->visitInitializer(InitExpr))
       return false;
 
@@ -5880,8 +5965,9 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
   const Record *R = this->getRecord(RD);
   if (!R)
     return false;
+  bool IsUnion = R->isUnion();
 
-  if (R->isUnion() && Ctor->isCopyOrMoveConstructor()) {
+  if (IsUnion && Ctor->isCopyOrMoveConstructor()) {
     if (R->getNumFields() == 0)
       return this->emitRetVoid(Ctor);
     // union copy and move ctors are special.
@@ -5908,7 +5994,7 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
     if (const FieldDecl *Member = Init->getMember()) {
       const Record::Field *F = R->getField(Member);
 
-      if (!emitFieldInitializer(F, F->Offset, InitExpr))
+      if (!emitFieldInitializer(F, F->Offset, InitExpr, IsUnion))
         return false;
     } else if (const Type *Base = Init->getBaseClass()) {
       const auto *BaseDecl = Base->getAsCXXRecordDecl();
@@ -5928,11 +6014,15 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
           return false;
       }
 
+      if (IsUnion && !this->emitActivate(InitExpr))
+        return false;
+
       if (!this->visitInitializer(InitExpr))
         return false;
       if (!this->emitFinishInitPop(InitExpr))
         return false;
     } else if (const IndirectFieldDecl *IFD = Init->getIndirectMember()) {
+
       assert(IFD->getChainingSize() >= 2);
 
       unsigned NestedFieldOffset = 0;
@@ -5944,12 +6034,14 @@ bool Compiler<Emitter>::compileConstructor(const CXXConstructorDecl *Ctor) {
 
         NestedField = FieldRecord->getField(FD);
         assert(NestedField);
+        IsUnion = IsUnion || FieldRecord->isUnion();
 
         NestedFieldOffset += NestedField->Offset;
       }
       assert(NestedField);
 
-      if (!emitFieldInitializer(NestedField, NestedFieldOffset, InitExpr))
+      if (!emitFieldInitializer(NestedField, NestedFieldOffset, InitExpr,
+                                IsUnion))
         return false;
 
       // Mark all chain links as initialized.