lib/AST/ByteCode/EvalEmitter.cpp - llvm-project/clang - Git at Google

 //===--- EvalEmitter.cpp - Instruction emitter for the VM -------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//

 #include "EvalEmitter.h"
 #include "Context.h"
 #include "IntegralAP.h"
 #include "Interp.h"
 #include "clang/AST/DeclCXX.h"

 using namespace clang;
 using namespace clang::interp;

 EvalEmitter::EvalEmitter(Context &Ctx, Program &P, State &Parent,
                          InterpStack &Stk)
     : Ctx(Ctx), P(P), S(Parent, P, Stk, Ctx, this), EvalResult(&Ctx) {}

 EvalEmitter::~EvalEmitter() {
   for (auto &V : Locals) {
     Block *B = reinterpret_cast<Block *>(V.get());
     if (B->isInitialized())
       B->invokeDtor();
   }
 }

 /// Clean up all our resources. This needs to done in failed evaluations before
 /// we call InterpStack::clear(), because there might be a Pointer on the stack
 /// pointing into a Block in the EvalEmitter.
 void EvalEmitter::cleanup() { S.cleanup(); }

 EvaluationResult EvalEmitter::interpretExpr(const Expr *E,
                                             bool ConvertResultToRValue,
                                             bool DestroyToplevelScope) {
   S.setEvalLocation(E->getExprLoc());
   this->ConvertResultToRValue = ConvertResultToRValue && !isa<ConstantExpr>(E);
   this->CheckFullyInitialized = isa<ConstantExpr>(E);
   EvalResult.setSource(E);

   if (!this->visitExpr(E, DestroyToplevelScope)) {
     // EvalResult may already have a result set, but something failed
     // after that (e.g. evaluating destructors).
     EvalResult.setInvalid();
   }

   return std::move(this->EvalResult);
 }

 EvaluationResult EvalEmitter::interpretDecl(const VarDecl *VD,
                                             bool CheckFullyInitialized) {
   this->CheckFullyInitialized = CheckFullyInitialized;
   S.EvaluatingDecl = VD;
   S.setEvalLocation(VD->getLocation());
   EvalResult.setSource(VD);

   if (const Expr *Init = VD->getAnyInitializer()) {
     QualType T = VD->getType();
     this->ConvertResultToRValue = !Init->isGLValue() && !T->isPointerType() &&
                                   !T->isObjCObjectPointerType();
   } else
     this->ConvertResultToRValue = false;

   EvalResult.setSource(VD);

   if (!this->visitDeclAndReturn(VD, S.inConstantContext()))
     EvalResult.setInvalid();

   S.EvaluatingDecl = nullptr;
   updateGlobalTemporaries();
   return std::move(this->EvalResult);
 }

 EvaluationResult EvalEmitter::interpretAsPointer(const Expr *E,
                                                  PtrCallback PtrCB) {

   S.setEvalLocation(E->getExprLoc());
   this->ConvertResultToRValue = false;
   this->CheckFullyInitialized = false;
   this->PtrCB = PtrCB;
   EvalResult.setSource(E);

   if (!this->visitExpr(E, /*DestroyToplevelScope=*/true)) {
     // EvalResult may already have a result set, but something failed
     // after that (e.g. evaluating destructors).
     EvalResult.setInvalid();
   }

   return std::move(this->EvalResult);
 }

 bool EvalEmitter::interpretCall(const FunctionDecl *FD, const Expr *E) {
   // Add parameters to the parameter map. The values in the ParamOffset don't
   // matter in this case as reading from them can't ever work.
   for (const ParmVarDecl *PD : FD->parameters()) {
     this->Params.insert({PD, {0, false}});
   }

   return this->visitExpr(E, /*DestroyToplevelScope=*/false);
 }

 void EvalEmitter::emitLabel(LabelTy Label) { CurrentLabel = Label; }

 EvalEmitter::LabelTy EvalEmitter::getLabel() { return NextLabel++; }

 Scope::Local EvalEmitter::createLocal(Descriptor *D) {
   // Allocate memory for a local.
   auto Memory = std::make_unique<char[]>(sizeof(Block) + D->getAllocSize());
   auto *B = new (Memory.get()) Block(Ctx.getEvalID(), D, /*isStatic=*/false);
   B->invokeCtor();

   // Initialize local variable inline descriptor.
   InlineDescriptor &Desc = *reinterpret_cast<InlineDescriptor *>(B->rawData());
   Desc.Desc = D;
   Desc.Offset = sizeof(InlineDescriptor);
   Desc.IsActive = true;
   Desc.IsBase = false;
   Desc.IsFieldMutable = false;
   Desc.IsConst = false;
   Desc.IsInitialized = false;

   // Register the local.
   unsigned Off = Locals.size();
   Locals.push_back(std::move(Memory));
   return {Off, D};
 }

 bool EvalEmitter::jumpTrue(const LabelTy &Label) {
   if (isActive()) {
     if (S.Stk.pop<bool>())
       ActiveLabel = Label;
   }
   return true;
 }

 bool EvalEmitter::jumpFalse(const LabelTy &Label) {
   if (isActive()) {
     if (!S.Stk.pop<bool>())
       ActiveLabel = Label;
   }
   return true;
 }

 bool EvalEmitter::jump(const LabelTy &Label) {
   if (isActive())
     CurrentLabel = ActiveLabel = Label;
   return true;
 }

 bool EvalEmitter::fallthrough(const LabelTy &Label) {
   if (isActive())
     ActiveLabel = Label;
   CurrentLabel = Label;
   return true;
 }

 bool EvalEmitter::speculate(const CallExpr *E, const LabelTy &EndLabel) {
   size_t StackSizeBefore = S.Stk.size();
   const Expr *Arg = E->getArg(0);
   if (!this->visit(Arg)) {
     S.Stk.clearTo(StackSizeBefore);

     if (S.inConstantContext() || Arg->HasSideEffects(S.getASTContext()))
       return this->emitBool(false, E);
     return Invalid(S, OpPC);
   }

   PrimType T = Ctx.classify(Arg->getType()).value_or(PT_Ptr);
   if (T == PT_Ptr) {
     const auto &Ptr = S.Stk.pop<Pointer>();
     return this->emitBool(CheckBCPResult(S, Ptr), E);
   }

   // Otherwise, this is fine!
   if (!this->emitPop(T, E))
     return false;
   return this->emitBool(true, E);
 }

 template <PrimType OpType> bool EvalEmitter::emitRet(const SourceInfo &Info) {
   if (!isActive())
     return true;

   using T = typename PrimConv<OpType>::T;
   EvalResult.takeValue(S.Stk.pop<T>().toAPValue(Ctx.getASTContext()));
   return true;
 }

 template <> bool EvalEmitter::emitRet<PT_Ptr>(const SourceInfo &Info) {
   if (!isActive())
     return true;

   const Pointer &Ptr = S.Stk.pop<Pointer>();

   if (Ptr.isFunctionPointer()) {
     EvalResult.takeValue(Ptr.toAPValue(Ctx.getASTContext()));
     return true;
   }

   // If we're returning a raw pointer, call our callback.
   if (this->PtrCB)
     return (*this->PtrCB)(Ptr);

   if (!EvalResult.checkReturnValue(S, Ctx, Ptr, Info))
     return false;
   if (CheckFullyInitialized && !EvalResult.checkFullyInitialized(S, Ptr))
     return false;

   // Implicitly convert lvalue to rvalue, if requested.
   if (ConvertResultToRValue) {
     if (!Ptr.isZero() && !Ptr.isDereferencable())
       return false;

     if (Ptr.pointsToStringLiteral() && Ptr.isArrayRoot())
       return false;

     if (!Ptr.isZero() && !CheckFinalLoad(S, OpPC, Ptr))
       return false;

     // Never allow reading from a non-const pointer, unless the memory
     // has been created in this evaluation.
     if (!Ptr.isZero() && !Ptr.isConst() && Ptr.isBlockPointer() &&
         Ptr.block()->getEvalID() != Ctx.getEvalID())
       return false;

     if (std::optional<APValue> V =
             Ptr.toRValue(Ctx, EvalResult.getSourceType())) {
       EvalResult.takeValue(std::move(*V));
     } else {
       return false;
     }
   } else {
     // If this is pointing to a local variable, just return
     // the result, even if the pointer is dead.
     // This will later be diagnosed by CheckLValueConstantExpression.
     if (Ptr.isBlockPointer() && !Ptr.block()->isStatic()) {
       EvalResult.takeValue(Ptr.toAPValue(Ctx.getASTContext()));
       return true;
     }

     if (!Ptr.isLive() && !Ptr.isTemporary())
       return false;

     EvalResult.takeValue(Ptr.toAPValue(Ctx.getASTContext()));
   }

   return true;
 }

 bool EvalEmitter::emitRetVoid(const SourceInfo &Info) {
   EvalResult.setValid();
   return true;
 }

 bool EvalEmitter::emitRetValue(const SourceInfo &Info) {
   const auto &Ptr = S.Stk.pop<Pointer>();

   if (!EvalResult.checkReturnValue(S, Ctx, Ptr, Info))
     return false;
   if (CheckFullyInitialized && !EvalResult.checkFullyInitialized(S, Ptr))
     return false;

   if (std::optional<APValue> APV =
           Ptr.toRValue(S.getASTContext(), EvalResult.getSourceType())) {
     EvalResult.takeValue(std::move(*APV));
     return true;
   }

   EvalResult.setInvalid();
   return false;
 }

 bool EvalEmitter::emitGetPtrLocal(uint32_t I, const SourceInfo &Info) {
   if (!isActive())
     return true;

   Block *B = getLocal(I);
   S.Stk.push<Pointer>(B, sizeof(InlineDescriptor));
   return true;
 }

 template <PrimType OpType>
 bool EvalEmitter::emitGetLocal(uint32_t I, const SourceInfo &Info) {
   if (!isActive())
     return true;

   using T = typename PrimConv<OpType>::T;

   Block *B = getLocal(I);

   if (!CheckLocalLoad(S, OpPC, B))
     return false;

   S.Stk.push<T>(*reinterpret_cast<T *>(B->data()));
   return true;
 }

 template <PrimType OpType>
 bool EvalEmitter::emitSetLocal(uint32_t I, const SourceInfo &Info) {
   if (!isActive())
     return true;

   using T = typename PrimConv<OpType>::T;

   Block *B = getLocal(I);
   *reinterpret_cast<T *>(B->data()) = S.Stk.pop<T>();
   InlineDescriptor &Desc = *reinterpret_cast<InlineDescriptor *>(B->rawData());
   Desc.IsInitialized = true;

   return true;
 }

 bool EvalEmitter::emitDestroy(uint32_t I, const SourceInfo &Info) {
   if (!isActive())
     return true;

   for (auto &Local : Descriptors[I]) {
     Block *B = getLocal(Local.Offset);
     S.deallocate(B);
   }

   return true;
 }

 /// Global temporaries (LifetimeExtendedTemporary) carry their value
 /// around as an APValue, which codegen accesses.
 /// We set their value once when creating them, but we don't update it
 /// afterwards when code changes it later.
 /// This is what we do here.
 void EvalEmitter::updateGlobalTemporaries() {
   for (const auto &[E, Temp] : S.SeenGlobalTemporaries) {
     UnsignedOrNone GlobalIndex = P.getGlobal(E);
     assert(GlobalIndex);
     const Pointer &Ptr = P.getPtrGlobal(*GlobalIndex);
     APValue *Cached = Temp->getOrCreateValue(true);
     if (OptPrimType T = Ctx.classify(E->getType())) {
       TYPE_SWITCH(*T,
                   { *Cached = Ptr.deref<T>().toAPValue(Ctx.getASTContext()); });
     } else {
       if (std::optional<APValue> APV =
               Ptr.toRValue(Ctx, Temp->getTemporaryExpr()->getType()))
         *Cached = *APV;
     }
   }
   S.SeenGlobalTemporaries.clear();
 }

 //===----------------------------------------------------------------------===//
 // Opcode evaluators
 //===----------------------------------------------------------------------===//

 #define GET_EVAL_IMPL
 #include "Opcodes.inc"
 #undef GET_EVAL_IMPL
	//===--- EvalEmitter.cpp - Instruction emitter for the VM -------- C++ --===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//

	#include "EvalEmitter.h"
	#include "Context.h"
	#include "IntegralAP.h"
	#include "Interp.h"
	#include "clang/AST/DeclCXX.h"

	using namespace clang;
	using namespace clang::interp;

	EvalEmitter::EvalEmitter(Context &Ctx, Program &P, State &Parent,
	InterpStack &Stk)
	: Ctx(Ctx), P(P), S(Parent, P, Stk, Ctx, this), EvalResult(&Ctx) {}

	EvalEmitter::~EvalEmitter() {
	for (auto &V : Locals) {
	Block B = reinterpret_cast<Block >(V.get());
	if (B->isInitialized())
	B->invokeDtor();
	}
	}

	/// Clean up all our resources. This needs to done in failed evaluations before
	/// we call InterpStack::clear(), because there might be a Pointer on the stack
	/// pointing into a Block in the EvalEmitter.
	void EvalEmitter::cleanup() { S.cleanup(); }

	EvaluationResult EvalEmitter::interpretExpr(const Expr *E,
	bool ConvertResultToRValue,
	bool DestroyToplevelScope) {
	S.setEvalLocation(E->getExprLoc());
	this->ConvertResultToRValue = ConvertResultToRValue && !isa<ConstantExpr>(E);
	this->CheckFullyInitialized = isa<ConstantExpr>(E);
	EvalResult.setSource(E);

	if (!this->visitExpr(E, DestroyToplevelScope)) {
	// EvalResult may already have a result set, but something failed
	// after that (e.g. evaluating destructors).
	EvalResult.setInvalid();
	}

	return std::move(this->EvalResult);
	}

	EvaluationResult EvalEmitter::interpretDecl(const VarDecl *VD,
	bool CheckFullyInitialized) {
	this->CheckFullyInitialized = CheckFullyInitialized;
	S.EvaluatingDecl = VD;
	S.setEvalLocation(VD->getLocation());
	EvalResult.setSource(VD);

	if (const Expr *Init = VD->getAnyInitializer()) {
	QualType T = VD->getType();
	this->ConvertResultToRValue = !Init->isGLValue() && !T->isPointerType() &&
	!T->isObjCObjectPointerType();
	} else
	this->ConvertResultToRValue = false;

	EvalResult.setSource(VD);

	if (!this->visitDeclAndReturn(VD, S.inConstantContext()))
	EvalResult.setInvalid();

	S.EvaluatingDecl = nullptr;
	updateGlobalTemporaries();
	return std::move(this->EvalResult);
	}

	EvaluationResult EvalEmitter::interpretAsPointer(const Expr *E,
	PtrCallback PtrCB) {

	S.setEvalLocation(E->getExprLoc());
	this->ConvertResultToRValue = false;
	this->CheckFullyInitialized = false;
	this->PtrCB = PtrCB;
	EvalResult.setSource(E);

	if (!this->visitExpr(E, /DestroyToplevelScope=/true)) {
	// EvalResult may already have a result set, but something failed
	// after that (e.g. evaluating destructors).
	EvalResult.setInvalid();
	}

	return std::move(this->EvalResult);
	}

	bool EvalEmitter::interpretCall(const FunctionDecl FD, const Expr E) {
	// Add parameters to the parameter map. The values in the ParamOffset don't
	// matter in this case as reading from them can't ever work.
	for (const ParmVarDecl *PD : FD->parameters()) {
	this->Params.insert({PD, {0, false}});
	}

	return this->visitExpr(E, /DestroyToplevelScope=/false);
	}

	void EvalEmitter::emitLabel(LabelTy Label) { CurrentLabel = Label; }

	EvalEmitter::LabelTy EvalEmitter::getLabel() { return NextLabel++; }

	Scope::Local EvalEmitter::createLocal(Descriptor *D) {
	// Allocate memory for a local.
	auto Memory = std::make_unique<char[]>(sizeof(Block) + D->getAllocSize());
	auto B = new (Memory.get()) Block(Ctx.getEvalID(), D, /isStatic=*/false);
	B->invokeCtor();

	// Initialize local variable inline descriptor.
	InlineDescriptor &Desc = reinterpret_cast<InlineDescriptor >(B->rawData());
	Desc.Desc = D;
	Desc.Offset = sizeof(InlineDescriptor);
	Desc.IsActive = true;
	Desc.IsBase = false;
	Desc.IsFieldMutable = false;
	Desc.IsConst = false;
	Desc.IsInitialized = false;

	// Register the local.
	unsigned Off = Locals.size();
	Locals.push_back(std::move(Memory));
	return {Off, D};
	}

	bool EvalEmitter::jumpTrue(const LabelTy &Label) {
	if (isActive()) {
	if (S.Stk.pop<bool>())
	ActiveLabel = Label;
	}
	return true;
	}

	bool EvalEmitter::jumpFalse(const LabelTy &Label) {
	if (isActive()) {
	if (!S.Stk.pop<bool>())
	ActiveLabel = Label;
	}
	return true;
	}

	bool EvalEmitter::jump(const LabelTy &Label) {
	if (isActive())
	CurrentLabel = ActiveLabel = Label;
	return true;
	}

	bool EvalEmitter::fallthrough(const LabelTy &Label) {
	if (isActive())
	ActiveLabel = Label;
	CurrentLabel = Label;
	return true;
	}

	bool EvalEmitter::speculate(const CallExpr *E, const LabelTy &EndLabel) {
	size_t StackSizeBefore = S.Stk.size();
	const Expr *Arg = E->getArg(0);
	if (!this->visit(Arg)) {
	S.Stk.clearTo(StackSizeBefore);

	if (S.inConstantContext() \|\| Arg->HasSideEffects(S.getASTContext()))
	return this->emitBool(false, E);
	return Invalid(S, OpPC);
	}

	PrimType T = Ctx.classify(Arg->getType()).value_or(PT_Ptr);
	if (T == PT_Ptr) {
	const auto &Ptr = S.Stk.pop<Pointer>();
	return this->emitBool(CheckBCPResult(S, Ptr), E);
	}

	// Otherwise, this is fine!
	if (!this->emitPop(T, E))
	return false;
	return this->emitBool(true, E);
	}

	template <PrimType OpType> bool EvalEmitter::emitRet(const SourceInfo &Info) {
	if (!isActive())
	return true;

	using T = typename PrimConv<OpType>::T;
	EvalResult.takeValue(S.Stk.pop<T>().toAPValue(Ctx.getASTContext()));
	return true;
	}

	template <> bool EvalEmitter::emitRet<PT_Ptr>(const SourceInfo &Info) {
	if (!isActive())
	return true;

	const Pointer &Ptr = S.Stk.pop<Pointer>();

	if (Ptr.isFunctionPointer()) {
	EvalResult.takeValue(Ptr.toAPValue(Ctx.getASTContext()));
	return true;
	}

	// If we're returning a raw pointer, call our callback.
	if (this->PtrCB)
	return (*this->PtrCB)(Ptr);

	if (!EvalResult.checkReturnValue(S, Ctx, Ptr, Info))
	return false;
	if (CheckFullyInitialized && !EvalResult.checkFullyInitialized(S, Ptr))
	return false;

	// Implicitly convert lvalue to rvalue, if requested.
	if (ConvertResultToRValue) {
	if (!Ptr.isZero() && !Ptr.isDereferencable())
	return false;

	if (Ptr.pointsToStringLiteral() && Ptr.isArrayRoot())
	return false;

	if (!Ptr.isZero() && !CheckFinalLoad(S, OpPC, Ptr))
	return false;

	// Never allow reading from a non-const pointer, unless the memory
	// has been created in this evaluation.
	if (!Ptr.isZero() && !Ptr.isConst() && Ptr.isBlockPointer() &&
	Ptr.block()->getEvalID() != Ctx.getEvalID())
	return false;

	if (std::optional<APValue> V =
	Ptr.toRValue(Ctx, EvalResult.getSourceType())) {
	EvalResult.takeValue(std::move(*V));
	} else {
	return false;
	}
	} else {
	// If this is pointing to a local variable, just return
	// the result, even if the pointer is dead.
	// This will later be diagnosed by CheckLValueConstantExpression.
	if (Ptr.isBlockPointer() && !Ptr.block()->isStatic()) {
	EvalResult.takeValue(Ptr.toAPValue(Ctx.getASTContext()));
	return true;
	}

	if (!Ptr.isLive() && !Ptr.isTemporary())
	return false;

	EvalResult.takeValue(Ptr.toAPValue(Ctx.getASTContext()));
	}

	return true;
	}

	bool EvalEmitter::emitRetVoid(const SourceInfo &Info) {
	EvalResult.setValid();
	return true;
	}

	bool EvalEmitter::emitRetValue(const SourceInfo &Info) {
	const auto &Ptr = S.Stk.pop<Pointer>();

	if (!EvalResult.checkReturnValue(S, Ctx, Ptr, Info))
	return false;
	if (CheckFullyInitialized && !EvalResult.checkFullyInitialized(S, Ptr))
	return false;

	if (std::optional<APValue> APV =
	Ptr.toRValue(S.getASTContext(), EvalResult.getSourceType())) {
	EvalResult.takeValue(std::move(*APV));
	return true;
	}

	EvalResult.setInvalid();
	return false;
	}

	bool EvalEmitter::emitGetPtrLocal(uint32_t I, const SourceInfo &Info) {
	if (!isActive())
	return true;

	Block *B = getLocal(I);
	S.Stk.push<Pointer>(B, sizeof(InlineDescriptor));
	return true;
	}

	template <PrimType OpType>
	bool EvalEmitter::emitGetLocal(uint32_t I, const SourceInfo &Info) {
	if (!isActive())
	return true;

	using T = typename PrimConv<OpType>::T;

	Block *B = getLocal(I);

	if (!CheckLocalLoad(S, OpPC, B))
	return false;

	S.Stk.push<T>(reinterpret_cast<T >(B->data()));
	return true;
	}

	template <PrimType OpType>
	bool EvalEmitter::emitSetLocal(uint32_t I, const SourceInfo &Info) {
	if (!isActive())
	return true;

	using T = typename PrimConv<OpType>::T;

	Block *B = getLocal(I);
	reinterpret_cast<T >(B->data()) = S.Stk.pop<T>();
	InlineDescriptor &Desc = reinterpret_cast<InlineDescriptor >(B->rawData());
	Desc.IsInitialized = true;

	return true;
	}

	bool EvalEmitter::emitDestroy(uint32_t I, const SourceInfo &Info) {
	if (!isActive())
	return true;

	for (auto &Local : Descriptors[I]) {
	Block *B = getLocal(Local.Offset);
	S.deallocate(B);
	}

	return true;
	}

	/// Global temporaries (LifetimeExtendedTemporary) carry their value
	/// around as an APValue, which codegen accesses.
	/// We set their value once when creating them, but we don't update it
	/// afterwards when code changes it later.
	/// This is what we do here.
	void EvalEmitter::updateGlobalTemporaries() {
	for (const auto &[E, Temp] : S.SeenGlobalTemporaries) {
	UnsignedOrNone GlobalIndex = P.getGlobal(E);
	assert(GlobalIndex);
	const Pointer &Ptr = P.getPtrGlobal(*GlobalIndex);
	APValue *Cached = Temp->getOrCreateValue(true);
	if (OptPrimType T = Ctx.classify(E->getType())) {
	TYPE_SWITCH(*T,
	{ *Cached = Ptr.deref<T>().toAPValue(Ctx.getASTContext()); });
	} else {
	if (std::optional<APValue> APV =
	Ptr.toRValue(Ctx, Temp->getTemporaryExpr()->getType()))
	Cached = APV;
	}
	}
	S.SeenGlobalTemporaries.clear();
	}

	//===----------------------------------------------------------------------===//
	// Opcode evaluators
	//===----------------------------------------------------------------------===//

	#define GET_EVAL_IMPL
	#include "Opcodes.inc"
	#undef GET_EVAL_IMPL