[Clang Interpreter] Initial patch for the constexpr interpreter
Summary:
This patch introduces the skeleton of the constexpr interpreter,
capable of evaluating a simple constexpr functions consisting of
if statements. The interpreter is described in more detail in the
RFC. Further patches will add more features.
Reviewers: Bigcheese, jfb, rsmith
Subscribers: bruno, uenoku, ldionne, Tyker, thegameg, tschuett, dexonsmith, mgorny, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D64146
llvm-svn: 371834
diff --git a/clang/lib/AST/Interp/ByteCodeStmtGen.cpp b/clang/lib/AST/Interp/ByteCodeStmtGen.cpp
new file mode 100644
index 0000000..c713015
--- /dev/null
+++ b/clang/lib/AST/Interp/ByteCodeStmtGen.cpp
@@ -0,0 +1,265 @@
+//===--- ByteCodeStmtGen.cpp - Code generator for expressions ---*- 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 "ByteCodeStmtGen.h"
+#include "ByteCodeEmitter.h"
+#include "ByteCodeGenError.h"
+#include "Context.h"
+#include "Function.h"
+#include "PrimType.h"
+#include "Program.h"
+#include "State.h"
+
+using namespace clang;
+using namespace clang::interp;
+
+template <typename T> using Expected = llvm::Expected<T>;
+template <typename T> using Optional = llvm::Optional<T>;
+
+namespace clang {
+namespace interp {
+
+/// Scope managing label targets.
+template <class Emitter> class LabelScope {
+public:
+ virtual ~LabelScope() { }
+
+protected:
+ LabelScope(ByteCodeStmtGen<Emitter> *Ctx) : Ctx(Ctx) {}
+ /// ByteCodeStmtGen instance.
+ ByteCodeStmtGen<Emitter> *Ctx;
+};
+
+/// Sets the context for break/continue statements.
+template <class Emitter> class LoopScope final : public LabelScope<Emitter> {
+public:
+ using LabelTy = typename ByteCodeStmtGen<Emitter>::LabelTy;
+ using OptLabelTy = typename ByteCodeStmtGen<Emitter>::OptLabelTy;
+
+ LoopScope(ByteCodeStmtGen<Emitter> *Ctx, LabelTy BreakLabel,
+ LabelTy ContinueLabel)
+ : LabelScope<Emitter>(Ctx), OldBreakLabel(Ctx->BreakLabel),
+ OldContinueLabel(Ctx->ContinueLabel) {
+ this->Ctx->BreakLabel = BreakLabel;
+ this->Ctx->ContinueLabel = ContinueLabel;
+ }
+
+ ~LoopScope() {
+ this->Ctx->BreakLabel = OldBreakLabel;
+ this->Ctx->ContinueLabel = OldContinueLabel;
+ }
+
+private:
+ OptLabelTy OldBreakLabel;
+ OptLabelTy OldContinueLabel;
+};
+
+// Sets the context for a switch scope, mapping labels.
+template <class Emitter> class SwitchScope final : public LabelScope<Emitter> {
+public:
+ using LabelTy = typename ByteCodeStmtGen<Emitter>::LabelTy;
+ using OptLabelTy = typename ByteCodeStmtGen<Emitter>::OptLabelTy;
+ using CaseMap = typename ByteCodeStmtGen<Emitter>::CaseMap;
+
+ SwitchScope(ByteCodeStmtGen<Emitter> *Ctx, CaseMap &&CaseLabels,
+ LabelTy BreakLabel, OptLabelTy DefaultLabel)
+ : LabelScope<Emitter>(Ctx), OldBreakLabel(Ctx->BreakLabel),
+ OldDefaultLabel(this->Ctx->DefaultLabel),
+ OldCaseLabels(std::move(this->Ctx->CaseLabels)) {
+ this->Ctx->BreakLabel = BreakLabel;
+ this->Ctx->DefaultLabel = DefaultLabel;
+ this->Ctx->CaseLabels = std::move(CaseLabels);
+ }
+
+ ~SwitchScope() {
+ this->Ctx->BreakLabel = OldBreakLabel;
+ this->Ctx->DefaultLabel = OldDefaultLabel;
+ this->Ctx->CaseLabels = std::move(OldCaseLabels);
+ }
+
+private:
+ OptLabelTy OldBreakLabel;
+ OptLabelTy OldDefaultLabel;
+ CaseMap OldCaseLabels;
+};
+
+} // namespace interp
+} // namespace clang
+
+template <class Emitter>
+bool ByteCodeStmtGen<Emitter>::visitFunc(const FunctionDecl *F) {
+ // Classify the return type.
+ ReturnType = this->classify(F->getReturnType());
+
+ // Set up fields and context if a constructor.
+ if (auto *MD = dyn_cast<CXXMethodDecl>(F))
+ return this->bail(MD);
+
+ if (auto *Body = F->getBody())
+ if (!visitStmt(Body))
+ return false;
+
+ // Emit a guard return to protect against a code path missing one.
+ if (F->getReturnType()->isVoidType())
+ return this->emitRetVoid(SourceInfo{});
+ else
+ return this->emitNoRet(SourceInfo{});
+}
+
+template <class Emitter>
+bool ByteCodeStmtGen<Emitter>::visitStmt(const Stmt *S) {
+ switch (S->getStmtClass()) {
+ case Stmt::CompoundStmtClass:
+ return visitCompoundStmt(cast<CompoundStmt>(S));
+ case Stmt::DeclStmtClass:
+ return visitDeclStmt(cast<DeclStmt>(S));
+ case Stmt::ReturnStmtClass:
+ return visitReturnStmt(cast<ReturnStmt>(S));
+ case Stmt::IfStmtClass:
+ return visitIfStmt(cast<IfStmt>(S));
+ case Stmt::NullStmtClass:
+ return true;
+ default: {
+ if (auto *Exp = dyn_cast<Expr>(S))
+ return this->discard(Exp);
+ return this->bail(S);
+ }
+ }
+}
+
+template <class Emitter>
+bool ByteCodeStmtGen<Emitter>::visitCompoundStmt(
+ const CompoundStmt *CompoundStmt) {
+ BlockScope<Emitter> Scope(this);
+ for (auto *InnerStmt : CompoundStmt->body())
+ if (!visitStmt(InnerStmt))
+ return false;
+ return true;
+}
+
+template <class Emitter>
+bool ByteCodeStmtGen<Emitter>::visitDeclStmt(const DeclStmt *DS) {
+ for (auto *D : DS->decls()) {
+ // Variable declarator.
+ if (auto *VD = dyn_cast<VarDecl>(D)) {
+ if (!visitVarDecl(VD))
+ return false;
+ continue;
+ }
+
+ // Decomposition declarator.
+ if (auto *DD = dyn_cast<DecompositionDecl>(D)) {
+ return this->bail(DD);
+ }
+ }
+
+ return true;
+}
+
+template <class Emitter>
+bool ByteCodeStmtGen<Emitter>::visitReturnStmt(const ReturnStmt *RS) {
+ if (const Expr *RE = RS->getRetValue()) {
+ ExprScope<Emitter> RetScope(this);
+ if (ReturnType) {
+ // Primitive types are simply returned.
+ if (!this->visit(RE))
+ return false;
+ this->emitCleanup();
+ return this->emitRet(*ReturnType, RS);
+ } else {
+ // RVO - construct the value in the return location.
+ auto ReturnLocation = [this, RE] { return this->emitGetParamPtr(0, RE); };
+ if (!this->visitInitializer(RE, ReturnLocation))
+ return false;
+ this->emitCleanup();
+ return this->emitRetVoid(RS);
+ }
+ } else {
+ this->emitCleanup();
+ if (!this->emitRetVoid(RS))
+ return false;
+ return true;
+ }
+}
+
+template <class Emitter>
+bool ByteCodeStmtGen<Emitter>::visitIfStmt(const IfStmt *IS) {
+ BlockScope<Emitter> IfScope(this);
+ if (auto *CondInit = IS->getInit())
+ if (!visitStmt(IS->getInit()))
+ return false;
+
+ if (const DeclStmt *CondDecl = IS->getConditionVariableDeclStmt())
+ if (!visitDeclStmt(CondDecl))
+ return false;
+
+ if (!this->visitBool(IS->getCond()))
+ return false;
+
+ if (const Stmt *Else = IS->getElse()) {
+ LabelTy LabelElse = this->getLabel();
+ LabelTy LabelEnd = this->getLabel();
+ if (!this->jumpFalse(LabelElse))
+ return false;
+ if (!visitStmt(IS->getThen()))
+ return false;
+ if (!this->jump(LabelEnd))
+ return false;
+ this->emitLabel(LabelElse);
+ if (!visitStmt(Else))
+ return false;
+ this->emitLabel(LabelEnd);
+ } else {
+ LabelTy LabelEnd = this->getLabel();
+ if (!this->jumpFalse(LabelEnd))
+ return false;
+ if (!visitStmt(IS->getThen()))
+ return false;
+ this->emitLabel(LabelEnd);
+ }
+
+ return true;
+}
+
+template <class Emitter>
+bool ByteCodeStmtGen<Emitter>::visitVarDecl(const VarDecl *VD) {
+ auto DT = VD->getType();
+
+ if (!VD->hasLocalStorage()) {
+ // No code generation required.
+ return true;
+ }
+
+ // Integers, pointers, primitives.
+ if (Optional<PrimType> T = this->classify(DT)) {
+ auto Off = this->allocateLocalPrimitive(VD, *T, DT.isConstQualified());
+ // Compile the initialiser in its own scope.
+ {
+ ExprScope<Emitter> Scope(this);
+ if (!this->visit(VD->getInit()))
+ return false;
+ }
+ // Set the value.
+ return this->emitSetLocal(*T, Off, VD);
+ } else {
+ // Composite types - allocate storage and initialize it.
+ if (auto Off = this->allocateLocal(VD)) {
+ return this->visitLocalInitializer(VD->getInit(), *Off);
+ } else {
+ return this->bail(VD);
+ }
+ }
+}
+
+namespace clang {
+namespace interp {
+
+template class ByteCodeStmtGen<ByteCodeEmitter>;
+
+} // namespace interp
+} // namespace clang