Coverage Report

Created: 2020-09-19 12:23

/Users/buildslave/jenkins/workspace/coverage/llvm-project/clang/lib/CodeGen/ConstantEmitter.h
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//===--- ConstantEmitter.h - IR constant emission ---------------*- 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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//
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// A helper class for emitting expressions and values as llvm::Constants
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// and as initializers for global variables.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_LIB_CODEGEN_CONSTANTEMITTER_H
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#define LLVM_CLANG_LIB_CODEGEN_CONSTANTEMITTER_H
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#include "CodeGenFunction.h"
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#include "CodeGenModule.h"
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namespace clang {
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namespace CodeGen {
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class ConstantEmitter {
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public:
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  CodeGenModule &CGM;
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  CodeGenFunction *const CGF;
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private:
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  bool Abstract = false;
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  /// Whether non-abstract components of the emitter have been initialized.
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  bool InitializedNonAbstract = false;
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  /// Whether the emitter has been finalized.
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  bool Finalized = false;
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  /// Whether the constant-emission failed.
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  bool Failed = false;
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  /// Whether we're in a constant context.
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  bool InConstantContext = false;
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  /// The AST address space where this (non-abstract) initializer is going.
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  /// Used for generating appropriate placeholders.
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  LangAS DestAddressSpace;
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  llvm::SmallVector<std::pair<llvm::Constant *, llvm::GlobalVariable*>, 4>
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    PlaceholderAddresses;
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public:
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  ConstantEmitter(CodeGenModule &CGM, CodeGenFunction *CGF = nullptr)
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    : CGM(CGM), CGF(CGF) {}
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  /// Initialize this emission in the context of the given function.
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  /// Use this if the expression might contain contextual references like
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  /// block addresses or PredefinedExprs.
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  ConstantEmitter(CodeGenFunction &CGF)
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    : CGM(CGF.CGM), CGF(&CGF) {}
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  ConstantEmitter(const ConstantEmitter &other) = delete;
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  ConstantEmitter &operator=(const ConstantEmitter &other) = delete;
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  ~ConstantEmitter();
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  /// Is the current emission context abstract?
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  bool isAbstract() const {
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    return Abstract;
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  }
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  /// Try to emit the initiaizer of the given declaration as an abstract
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  /// constant.  If this succeeds, the emission must be finalized.
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  llvm::Constant *tryEmitForInitializer(const VarDecl &D);
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  llvm::Constant *tryEmitForInitializer(const Expr *E, LangAS destAddrSpace,
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                                        QualType destType);
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  llvm::Constant *emitForInitializer(const APValue &value, LangAS destAddrSpace,
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                                     QualType destType);
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  void finalize(llvm::GlobalVariable *global);
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  // All of the "abstract" emission methods below permit the emission to
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  // be immediately discarded without finalizing anything.  Therefore, they
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  // must also promise not to do anything that will, in the future, require
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  // finalization:
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  //
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  //   - using the CGF (if present) for anything other than establishing
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  //     semantic context; for example, an expression with ignored
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  //     side-effects must not be emitted as an abstract expression
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  //
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  //   - doing anything that would not be safe to duplicate within an
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  //     initializer or to propagate to another context; for example,
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  //     side effects, or emitting an initialization that requires a
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  //     reference to its current location.
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  /// Try to emit the initializer of the given declaration as an abstract
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  /// constant.
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  llvm::Constant *tryEmitAbstractForInitializer(const VarDecl &D);
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  /// Emit the result of the given expression as an abstract constant,
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  /// asserting that it succeeded.  This is only safe to do when the
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  /// expression is known to be a constant expression with either a fairly
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  /// simple type or a known simple form.
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  llvm::Constant *emitAbstract(const Expr *E, QualType T);
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  llvm::Constant *emitAbstract(SourceLocation loc, const APValue &value,
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                               QualType T);
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  /// Try to emit the result of the given expression as an abstract constant.
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  llvm::Constant *tryEmitAbstract(const Expr *E, QualType T);
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  llvm::Constant *tryEmitAbstractForMemory(const Expr *E, QualType T);
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  llvm::Constant *tryEmitAbstract(const APValue &value, QualType T);
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  llvm::Constant *tryEmitAbstractForMemory(const APValue &value, QualType T);
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  llvm::Constant *tryEmitConstantExpr(const ConstantExpr *CE);
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  llvm::Constant *emitNullForMemory(QualType T) {
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    return emitNullForMemory(CGM, T);
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  }
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  llvm::Constant *emitForMemory(llvm::Constant *C, QualType T) {
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    return emitForMemory(CGM, C, T);
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  }
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  static llvm::Constant *emitNullForMemory(CodeGenModule &CGM, QualType T);
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  static llvm::Constant *emitForMemory(CodeGenModule &CGM, llvm::Constant *C,
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                                       QualType T);
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  // These are private helper routines of the constant emitter that
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  // can't actually be private because things are split out into helper
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  // functions and classes.
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  llvm::Constant *tryEmitPrivateForVarInit(const VarDecl &D);
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  llvm::Constant *tryEmitPrivate(const Expr *E, QualType T);
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  llvm::Constant *tryEmitPrivateForMemory(const Expr *E, QualType T);
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  llvm::Constant *tryEmitPrivate(const APValue &value, QualType T);
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  llvm::Constant *tryEmitPrivateForMemory(const APValue &value, QualType T);
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  /// Get the address of the current location.  This is a constant
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  /// that will resolve, after finalization, to the address of the
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  /// 'signal' value that is registered with the emitter later.
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  llvm::GlobalValue *getCurrentAddrPrivate();
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  /// Register a 'signal' value with the emitter to inform it where to
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  /// resolve a placeholder.  The signal value must be unique in the
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  /// initializer; it might, for example, be the address of a global that
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  /// refers to the current-address value in its own initializer.
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  ///
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  /// Uses of the placeholder must be properly anchored before finalizing
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  /// the emitter, e.g. by being installed as the initializer of a global
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  /// variable.  That is, it must be possible to replaceAllUsesWith
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  /// the placeholder with the proper address of the signal.
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  void registerCurrentAddrPrivate(llvm::Constant *signal,
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                                  llvm::GlobalValue *placeholder);
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private:
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  void initializeNonAbstract(LangAS destAS) {
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    assert(!InitializedNonAbstract);
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    InitializedNonAbstract = true;
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    DestAddressSpace = destAS;
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  }
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  llvm::Constant *markIfFailed(llvm::Constant *init) {
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    if (!init)
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      Failed = true;
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    return init;
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  }
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  struct AbstractState {
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    bool OldValue;
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    size_t OldPlaceholdersSize;
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  };
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  AbstractState pushAbstract() {
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    AbstractState saved = { Abstract, PlaceholderAddresses.size() };
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    Abstract = true;
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    return saved;
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  }
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  llvm::Constant *validateAndPopAbstract(llvm::Constant *C, AbstractState save);
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};
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}
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}
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#endif