ExternalFunctions.cpp | Explore in Territory

//===-- ExternalFunctions.cpp - Implement External Functions --------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
//  This file contains both code to deal with invoking "external" functions, but
//  also contains code that implements "exported" external functions.
//
//  There are currently two mechanisms for handling external functions in the
//  Interpreter.  The first is to implement lle_* wrapper functions that are
//  specific to well-known library functions which manually translate the
//  arguments from GenericValues and make the call.  If such a wrapper does
//  not exist, and libffi is available, then the Interpreter will attempt to
//  invoke the function using libffi, after finding its address.
//
//===----------------------------------------------------------------------===//

#include "Interpreter.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Config/config.h" // Detect libffi
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/DynamicLibrary.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cmath>
#include <csignal>
#include <cstdint>
#include <cstdio>
#include <cstring>
#include <map>
#include <mutex>
#include <string>
#include <utility>
#include <vector>

#ifdef HAVE_FFI_CALL
#ifdef HAVE_FFI_H
#include <ffi.h>
#define USE_LIBFFI
#elif HAVE_FFI_FFI_H
#include <ffi/ffi.h>
#define USE_LIBFFI
#endif
#endif

usingnamespacellvm;

namespace {

ExFunc;
RawFunc;

struct Functions { … };

Functions &getFunctions() { … }

} // anonymous namespace

static Interpreter *TheInterpreter;

static char getTypeID(Type *Ty) { … }

// Try to find address of external function given a Function object.
// Please note, that interpreter doesn't know how to assemble a
// real call in general case (this is JIT job), that's why it assumes,
// that all external functions has the same (and pretty "general") signature.
// The typical example of such functions are "lle_X_" ones.
static ExFunc lookupFunction(const Function *F) { … }

#ifdef USE_LIBFFI
static ffi_type *ffiTypeFor(Type *Ty) {
  switch (Ty->getTypeID()) {
    case Type::VoidTyID: return &ffi_type_void;
    case Type::IntegerTyID:
      switch (cast<IntegerType>(Ty)->getBitWidth()) {
        case 8:  return &ffi_type_sint8;
        case 16: return &ffi_type_sint16;
        case 32: return &ffi_type_sint32;
        case 64: return &ffi_type_sint64;
      }
      llvm_unreachable("Unhandled integer type bitwidth");
    case Type::FloatTyID:   return &ffi_type_float;
    case Type::DoubleTyID:  return &ffi_type_double;
    case Type::PointerTyID: return &ffi_type_pointer;
    default: break;
  }
  // TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
  report_fatal_error("Type could not be mapped for use with libffi.");
  return NULL;
}

static void *ffiValueFor(Type *Ty, const GenericValue &AV,
                         void *ArgDataPtr) {
  switch (Ty->getTypeID()) {
    case Type::IntegerTyID:
      switch (cast<IntegerType>(Ty)->getBitWidth()) {
        case 8: {
          int8_t *I8Ptr = (int8_t *) ArgDataPtr;
          *I8Ptr = (int8_t) AV.IntVal.getZExtValue();
          return ArgDataPtr;
        }
        case 16: {
          int16_t *I16Ptr = (int16_t *) ArgDataPtr;
          *I16Ptr = (int16_t) AV.IntVal.getZExtValue();
          return ArgDataPtr;
        }
        case 32: {
          int32_t *I32Ptr = (int32_t *) ArgDataPtr;
          *I32Ptr = (int32_t) AV.IntVal.getZExtValue();
          return ArgDataPtr;
        }
        case 64: {
          int64_t *I64Ptr = (int64_t *) ArgDataPtr;
          *I64Ptr = (int64_t) AV.IntVal.getZExtValue();
          return ArgDataPtr;
        }
      }
      llvm_unreachable("Unhandled integer type bitwidth");
    case Type::FloatTyID: {
      float *FloatPtr = (float *) ArgDataPtr;
      *FloatPtr = AV.FloatVal;
      return ArgDataPtr;
    }
    case Type::DoubleTyID: {
      double *DoublePtr = (double *) ArgDataPtr;
      *DoublePtr = AV.DoubleVal;
      return ArgDataPtr;
    }
    case Type::PointerTyID: {
      void **PtrPtr = (void **) ArgDataPtr;
      *PtrPtr = GVTOP(AV);
      return ArgDataPtr;
    }
    default: break;
  }
  // TODO: Support other types such as StructTyID, ArrayTyID, OpaqueTyID, etc.
  report_fatal_error("Type value could not be mapped for use with libffi.");
  return NULL;
}

static bool ffiInvoke(RawFunc Fn, Function *F, ArrayRef<GenericValue> ArgVals,
                      const DataLayout &TD, GenericValue &Result) {
  ffi_cif cif;
  FunctionType *FTy = F->getFunctionType();
  const unsigned NumArgs = F->arg_size();

  // TODO: We don't have type information about the remaining arguments, because
  // this information is never passed into ExecutionEngine::runFunction().
  if (ArgVals.size() > NumArgs && F->isVarArg()) {
    report_fatal_error("Calling external var arg function '" + F->getName()
                      + "' is not supported by the Interpreter.");
  }

  unsigned ArgBytes = 0;

  std::vector<ffi_type*> args(NumArgs);
  for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end();
       A != E; ++A) {
    const unsigned ArgNo = A->getArgNo();
    Type *ArgTy = FTy->getParamType(ArgNo);
    args[ArgNo] = ffiTypeFor(ArgTy);
    ArgBytes += TD.getTypeStoreSize(ArgTy);
  }

  SmallVector<uint8_t, 128> ArgData;
  ArgData.resize(ArgBytes);
  uint8_t *ArgDataPtr = ArgData.data();
  SmallVector<void*, 16> values(NumArgs);
  for (Function::const_arg_iterator A = F->arg_begin(), E = F->arg_end();
       A != E; ++A) {
    const unsigned ArgNo = A->getArgNo();
    Type *ArgTy = FTy->getParamType(ArgNo);
    values[ArgNo] = ffiValueFor(ArgTy, ArgVals[ArgNo], ArgDataPtr);
    ArgDataPtr += TD.getTypeStoreSize(ArgTy);
  }

  Type *RetTy = FTy->getReturnType();
  ffi_type *rtype = ffiTypeFor(RetTy);

  if (ffi_prep_cif(&cif, FFI_DEFAULT_ABI, NumArgs, rtype, args.data()) ==
      FFI_OK) {
    SmallVector<uint8_t, 128> ret;
    if (RetTy->getTypeID() != Type::VoidTyID)
      ret.resize(TD.getTypeStoreSize(RetTy));
    ffi_call(&cif, Fn, ret.data(), values.data());
    switch (RetTy->getTypeID()) {
      case Type::IntegerTyID:
        switch (cast<IntegerType>(RetTy)->getBitWidth()) {
          case 8:  Result.IntVal = APInt(8 , *(int8_t *) ret.data()); break;
          case 16: Result.IntVal = APInt(16, *(int16_t*) ret.data()); break;
          case 32: Result.IntVal = APInt(32, *(int32_t*) ret.data()); break;
          case 64: Result.IntVal = APInt(64, *(int64_t*) ret.data()); break;
        }
        break;
      case Type::FloatTyID:   Result.FloatVal   = *(float *) ret.data(); break;
      case Type::DoubleTyID:  Result.DoubleVal  = *(double*) ret.data(); break;
      case Type::PointerTyID: Result.PointerVal = *(void **) ret.data(); break;
      default: break;
    }
    return true;
  }

  return false;
}
#endif // USE_LIBFFI

GenericValue Interpreter::callExternalFunction(Function *F,
                                               ArrayRef<GenericValue> ArgVals) { … }

//===----------------------------------------------------------------------===//
//  Functions "exported" to the running application...
//

// void atexit(Function*)
static GenericValue lle_X_atexit(FunctionType *FT,
                                 ArrayRef<GenericValue> Args) { … }

// void exit(int)
static GenericValue lle_X_exit(FunctionType *FT, ArrayRef<GenericValue> Args) { … }

// void abort(void)
static GenericValue lle_X_abort(FunctionType *FT, ArrayRef<GenericValue> Args) { … }

// Silence warnings about sprintf. (See also
// https://github.com/llvm/llvm-project/issues/58086)
#if defined(__clang__)
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
#endif
// int sprintf(char *, const char *, ...) - a very rough implementation to make
// output useful.
static GenericValue lle_X_sprintf(FunctionType *FT,
                                  ArrayRef<GenericValue> Args) { … }
#if defined(__clang__)
#pragma clang diagnostic pop
#endif

// int printf(const char *, ...) - a very rough implementation to make output
// useful.
static GenericValue lle_X_printf(FunctionType *FT,
                                 ArrayRef<GenericValue> Args) { … }

// int sscanf(const char *format, ...);
static GenericValue lle_X_sscanf(FunctionType *FT,
                                 ArrayRef<GenericValue> args) { … }

// int scanf(const char *format, ...);
static GenericValue lle_X_scanf(FunctionType *FT, ArrayRef<GenericValue> args) { … }

// int fprintf(FILE *, const char *, ...) - a very rough implementation to make
// output useful.
static GenericValue lle_X_fprintf(FunctionType *FT,
                                  ArrayRef<GenericValue> Args) { … }

static GenericValue lle_X_memset(FunctionType *FT,
                                 ArrayRef<GenericValue> Args) { … }

static GenericValue lle_X_memcpy(FunctionType *FT,
                                 ArrayRef<GenericValue> Args) { … }

void Interpreter::initializeExternalFunctions() { … }
llvm/llvm/lib/ExecutionEngine/Interpreter/ExternalFunctions.cpp
