4e7cf1b1ed
Add an `EvaluationResult` class. This contains the result either as a `Pointer` or as a `APValue`. This way, we can inspect the result of the evaluation and diagnose problems with it (e.g. uninitialized fields in global initializers or pointers pointing to things they shouldn't point to).
272 lines
8.4 KiB
C++
272 lines
8.4 KiB
C++
//===--- ByteCodeEmitter.cpp - Instruction emitter for the VM ---*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#include "ByteCodeEmitter.h"
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#include "ByteCodeGenError.h"
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#include "Context.h"
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#include "Floating.h"
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#include "Opcode.h"
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#include "Program.h"
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#include "clang/AST/ASTLambda.h"
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#include "clang/AST/DeclCXX.h"
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#include "clang/Basic/Builtins.h"
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#include <type_traits>
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using namespace clang;
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using namespace clang::interp;
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Function *ByteCodeEmitter::compileFunc(const FunctionDecl *FuncDecl) {
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// Set up argument indices.
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unsigned ParamOffset = 0;
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SmallVector<PrimType, 8> ParamTypes;
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SmallVector<unsigned, 8> ParamOffsets;
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llvm::DenseMap<unsigned, Function::ParamDescriptor> ParamDescriptors;
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// If the return is not a primitive, a pointer to the storage where the
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// value is initialized in is passed as the first argument. See 'RVO'
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// elsewhere in the code.
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QualType Ty = FuncDecl->getReturnType();
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bool HasRVO = false;
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if (!Ty->isVoidType() && !Ctx.classify(Ty)) {
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HasRVO = true;
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ParamTypes.push_back(PT_Ptr);
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ParamOffsets.push_back(ParamOffset);
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ParamOffset += align(primSize(PT_Ptr));
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}
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// If the function decl is a member decl, the next parameter is
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// the 'this' pointer. This parameter is pop()ed from the
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// InterpStack when calling the function.
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bool HasThisPointer = false;
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if (const auto *MD = dyn_cast<CXXMethodDecl>(FuncDecl)) {
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if (MD->isImplicitObjectMemberFunction()) {
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HasThisPointer = true;
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ParamTypes.push_back(PT_Ptr);
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ParamOffsets.push_back(ParamOffset);
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ParamOffset += align(primSize(PT_Ptr));
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}
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// Set up lambda capture to closure record field mapping.
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if (isLambdaCallOperator(MD)) {
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const Record *R = P.getOrCreateRecord(MD->getParent());
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llvm::DenseMap<const ValueDecl *, FieldDecl *> LC;
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FieldDecl *LTC;
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MD->getParent()->getCaptureFields(LC, LTC);
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for (auto Cap : LC) {
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// Static lambdas cannot have any captures. If this one does,
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// it has already been diagnosed and we can only ignore it.
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if (MD->isStatic())
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return nullptr;
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unsigned Offset = R->getField(Cap.second)->Offset;
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this->LambdaCaptures[Cap.first] = {
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Offset, Cap.second->getType()->isReferenceType()};
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}
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if (LTC)
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this->LambdaThisCapture = R->getField(LTC)->Offset;
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}
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}
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// Assign descriptors to all parameters.
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// Composite objects are lowered to pointers.
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for (const ParmVarDecl *PD : FuncDecl->parameters()) {
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std::optional<PrimType> T = Ctx.classify(PD->getType());
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PrimType PT = T.value_or(PT_Ptr);
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Descriptor *Desc = P.createDescriptor(PD, PT);
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ParamDescriptors.insert({ParamOffset, {PT, Desc}});
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Params.insert({PD, {ParamOffset, T != std::nullopt}});
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ParamOffsets.push_back(ParamOffset);
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ParamOffset += align(primSize(PT));
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ParamTypes.push_back(PT);
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}
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// Create a handle over the emitted code.
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Function *Func = P.getFunction(FuncDecl);
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if (!Func) {
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bool IsUnevaluatedBuiltin = false;
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if (unsigned BI = FuncDecl->getBuiltinID())
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IsUnevaluatedBuiltin = Ctx.getASTContext().BuiltinInfo.isUnevaluated(BI);
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Func =
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P.createFunction(FuncDecl, ParamOffset, std::move(ParamTypes),
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std::move(ParamDescriptors), std::move(ParamOffsets),
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HasThisPointer, HasRVO, IsUnevaluatedBuiltin);
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}
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assert(Func);
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// For not-yet-defined functions, we only create a Function instance and
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// compile their body later.
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if (!FuncDecl->isDefined()) {
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Func->setDefined(false);
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return Func;
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}
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Func->setDefined(true);
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// Lambda static invokers are a special case that we emit custom code for.
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bool IsEligibleForCompilation = false;
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if (const auto *MD = dyn_cast<CXXMethodDecl>(FuncDecl))
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IsEligibleForCompilation = MD->isLambdaStaticInvoker();
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if (!IsEligibleForCompilation)
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IsEligibleForCompilation = FuncDecl->isConstexpr();
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// Compile the function body.
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if (!IsEligibleForCompilation || !visitFunc(FuncDecl)) {
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Func->setIsFullyCompiled(true);
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return Func;
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}
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// Create scopes from descriptors.
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llvm::SmallVector<Scope, 2> Scopes;
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for (auto &DS : Descriptors) {
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Scopes.emplace_back(std::move(DS));
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}
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// Set the function's code.
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Func->setCode(NextLocalOffset, std::move(Code), std::move(SrcMap),
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std::move(Scopes), FuncDecl->hasBody());
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Func->setIsFullyCompiled(true);
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return Func;
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}
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Scope::Local ByteCodeEmitter::createLocal(Descriptor *D) {
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NextLocalOffset += sizeof(Block);
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unsigned Location = NextLocalOffset;
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NextLocalOffset += align(D->getAllocSize());
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return {Location, D};
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}
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void ByteCodeEmitter::emitLabel(LabelTy Label) {
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const size_t Target = Code.size();
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LabelOffsets.insert({Label, Target});
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if (auto It = LabelRelocs.find(Label);
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It != LabelRelocs.end()) {
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for (unsigned Reloc : It->second) {
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using namespace llvm::support;
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// Rewrite the operand of all jumps to this label.
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void *Location = Code.data() + Reloc - align(sizeof(int32_t));
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assert(aligned(Location));
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const int32_t Offset = Target - static_cast<int64_t>(Reloc);
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endian::write<int32_t, llvm::endianness::native>(Location, Offset);
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}
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LabelRelocs.erase(It);
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}
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}
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int32_t ByteCodeEmitter::getOffset(LabelTy Label) {
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// Compute the PC offset which the jump is relative to.
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const int64_t Position =
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Code.size() + align(sizeof(Opcode)) + align(sizeof(int32_t));
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assert(aligned(Position));
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// If target is known, compute jump offset.
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if (auto It = LabelOffsets.find(Label);
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It != LabelOffsets.end())
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return It->second - Position;
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// Otherwise, record relocation and return dummy offset.
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LabelRelocs[Label].push_back(Position);
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return 0ull;
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}
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/// Helper to write bytecode and bail out if 32-bit offsets become invalid.
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/// Pointers will be automatically marshalled as 32-bit IDs.
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template <typename T>
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static void emit(Program &P, std::vector<std::byte> &Code, const T &Val,
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bool &Success) {
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size_t Size;
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if constexpr (std::is_pointer_v<T>)
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Size = sizeof(uint32_t);
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else
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Size = sizeof(T);
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if (Code.size() + Size > std::numeric_limits<unsigned>::max()) {
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Success = false;
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return;
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}
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// Access must be aligned!
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size_t ValPos = align(Code.size());
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Size = align(Size);
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assert(aligned(ValPos + Size));
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Code.resize(ValPos + Size);
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if constexpr (!std::is_pointer_v<T>) {
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new (Code.data() + ValPos) T(Val);
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} else {
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uint32_t ID = P.getOrCreateNativePointer(Val);
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new (Code.data() + ValPos) uint32_t(ID);
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}
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}
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template <>
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void emit(Program &P, std::vector<std::byte> &Code, const Floating &Val,
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bool &Success) {
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size_t Size = Val.bytesToSerialize();
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if (Code.size() + Size > std::numeric_limits<unsigned>::max()) {
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Success = false;
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return;
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}
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// Access must be aligned!
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size_t ValPos = align(Code.size());
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Size = align(Size);
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assert(aligned(ValPos + Size));
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Code.resize(ValPos + Size);
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Val.serialize(Code.data() + ValPos);
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}
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template <typename... Tys>
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bool ByteCodeEmitter::emitOp(Opcode Op, const Tys &... Args, const SourceInfo &SI) {
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bool Success = true;
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// The opcode is followed by arguments. The source info is
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// attached to the address after the opcode.
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emit(P, Code, Op, Success);
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if (SI)
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SrcMap.emplace_back(Code.size(), SI);
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// The initializer list forces the expression to be evaluated
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// for each argument in the variadic template, in order.
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(void)std::initializer_list<int>{(emit(P, Code, Args, Success), 0)...};
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return Success;
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}
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bool ByteCodeEmitter::jumpTrue(const LabelTy &Label) {
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return emitJt(getOffset(Label), SourceInfo{});
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}
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bool ByteCodeEmitter::jumpFalse(const LabelTy &Label) {
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return emitJf(getOffset(Label), SourceInfo{});
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}
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bool ByteCodeEmitter::jump(const LabelTy &Label) {
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return emitJmp(getOffset(Label), SourceInfo{});
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}
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bool ByteCodeEmitter::fallthrough(const LabelTy &Label) {
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emitLabel(Label);
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return true;
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}
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//===----------------------------------------------------------------------===//
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// Opcode emitters
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//===----------------------------------------------------------------------===//
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#define GET_LINK_IMPL
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#include "Opcodes.inc"
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#undef GET_LINK_IMPL
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