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      1 //===--- ByteCodeEmitter.h - Instruction emitter for the VM ---------*- C++ -*-===//
      2 //
      3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
      4 // See https://llvm.org/LICENSE.txt for license information.
      5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
      6 //
      7 //===----------------------------------------------------------------------===//
      8 //
      9 // Defines the instruction emitters.
     10 //
     11 //===----------------------------------------------------------------------===//
     12 
     13 #ifndef LLVM_CLANG_AST_INTERP_LINKEMITTER_H
     14 #define LLVM_CLANG_AST_INTERP_LINKEMITTER_H
     15 
     16 #include "ByteCodeGenError.h"
     17 #include "Context.h"
     18 #include "InterpStack.h"
     19 #include "InterpState.h"
     20 #include "PrimType.h"
     21 #include "Program.h"
     22 #include "Source.h"
     23 #include "llvm/Support/Error.h"
     24 
     25 namespace clang {
     26 namespace interp {
     27 class Context;
     28 class SourceInfo;
     29 enum Opcode : uint32_t;
     30 
     31 /// An emitter which links the program to bytecode for later use.
     32 class ByteCodeEmitter {
     33 protected:
     34   using LabelTy = uint32_t;
     35   using AddrTy = uintptr_t;
     36   using Local = Scope::Local;
     37 
     38 public:
     39   /// Compiles the function into the module.
     40   llvm::Expected<Function *> compileFunc(const FunctionDecl *F);
     41 
     42 protected:
     43   ByteCodeEmitter(Context &Ctx, Program &P) : Ctx(Ctx), P(P) {}
     44 
     45   virtual ~ByteCodeEmitter() {}
     46 
     47   /// Define a label.
     48   void emitLabel(LabelTy Label);
     49   /// Create a label.
     50   LabelTy getLabel() { return ++NextLabel; }
     51 
     52   /// Methods implemented by the compiler.
     53   virtual bool visitFunc(const FunctionDecl *E) = 0;
     54   virtual bool visitExpr(const Expr *E) = 0;
     55   virtual bool visitDecl(const VarDecl *E) = 0;
     56 
     57   /// Bails out if a given node cannot be compiled.
     58   bool bail(const Stmt *S) { return bail(S->getBeginLoc()); }
     59   bool bail(const Decl *D) { return bail(D->getBeginLoc()); }
     60   bool bail(const SourceLocation &Loc);
     61 
     62   /// Emits jumps.
     63   bool jumpTrue(const LabelTy &Label);
     64   bool jumpFalse(const LabelTy &Label);
     65   bool jump(const LabelTy &Label);
     66   bool fallthrough(const LabelTy &Label);
     67 
     68   /// Callback for local registration.
     69   Local createLocal(Descriptor *D);
     70 
     71   /// Parameter indices.
     72   llvm::DenseMap<const ParmVarDecl *, unsigned> Params;
     73   /// Local descriptors.
     74   llvm::SmallVector<SmallVector<Local, 8>, 2> Descriptors;
     75 
     76 private:
     77   /// Current compilation context.
     78   Context &Ctx;
     79   /// Program to link to.
     80   Program &P;
     81   /// Index of the next available label.
     82   LabelTy NextLabel = 0;
     83   /// Offset of the next local variable.
     84   unsigned NextLocalOffset = 0;
     85   /// Location of a failure.
     86   llvm::Optional<SourceLocation> BailLocation;
     87   /// Label information for linker.
     88   llvm::DenseMap<LabelTy, unsigned> LabelOffsets;
     89   /// Location of label relocations.
     90   llvm::DenseMap<LabelTy, llvm::SmallVector<unsigned, 5>> LabelRelocs;
     91   /// Program code.
     92   std::vector<char> Code;
     93   /// Opcode to expression mapping.
     94   SourceMap SrcMap;
     95 
     96   /// Returns the offset for a jump or records a relocation.
     97   int32_t getOffset(LabelTy Label);
     98 
     99   /// Emits an opcode.
    100   template <typename... Tys>
    101   bool emitOp(Opcode Op, const Tys &... Args, const SourceInfo &L);
    102 
    103 protected:
    104 #define GET_LINK_PROTO
    105 #include "Opcodes.inc"
    106 #undef GET_LINK_PROTO
    107 };
    108 
    109 } // namespace interp
    110 } // namespace clang
    111 
    112 #endif
    113