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//===-- BFtoLLVM.cpp - BF language Front End for LLVM ---------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is a simple front end for the BF language. It is compatible with the
// language as described in "The BrainF*** Language Specification (01 January
// 2002)", which is available from http://esoteric.sange.fi/ENSI . It does not
// implement the optional keyword # ("Output partial tape state").
//
//===----------------------------------------------------------------------===//
#include <iostream>
#include <vector>
#include <fstream>
#include <cerrno>
#include <cstring>
#include <string>
#include <cstdio>
#include <cassert>
void emitDeclarations(std::ofstream &dest) {
dest << "; This assembly code brought to you by BFtoLLVM\n"
<< "\nimplementation\n"
<< "\n; Declarations\n"
<< "\ndeclare int %getchar()\n"
<< "declare int %putchar(int)\n"
<< "declare void %llvm.memset.i32(sbyte*, ubyte, uint, uint)\n"
<< "\n";
}
void emitMainFunctionProlog(std::ofstream &dest) {
dest << "\n; Main function\n"
<< "int %main(int %argc, sbyte** %argv) {\n"
<< "\nentry:\n"
<< "%arr = alloca sbyte, uint 30000\n"
<< "call void (sbyte*, ubyte, uint, uint)* %llvm.memset.i32"
<< "(sbyte* %arr, ubyte 0, uint 30000, uint 1)\n"
<< "%ptrbox = alloca sbyte*\n"
<< "store sbyte* %arr, sbyte **%ptrbox\n"
<< "\n";
}
void emitMainFunctionEpilog(std::ofstream &dest) {
dest << "ret int 0\n"
<< "}\n";
}
std::string gensym (const std::string varName, bool percent = true) {
char buf[80];
static unsigned int SymbolCounter = 0;
sprintf (buf, "%s%s%u", percent ? "%" : "", varName.c_str(), SymbolCounter++);
return std::string (buf);
}
void emitArith (std::string op, char delta, std::ofstream &dest) {
std::string ptr = gensym (op + "ptr"),
val = gensym (op + "val"),
result = gensym (op + "result");
dest << ptr << " = load sbyte** %ptrbox\n"
<< val << " = load sbyte* " << ptr << "\n"
<< result << " = add sbyte " << val << ", " << (int)delta << "\n"
<< "store sbyte " << result << ", sbyte* " << ptr << "\n";
}
// + becomes ++*p; and - becomes --*p;
void emitPlus (std::ofstream &dest, int ct) { emitArith ("plus", +ct, dest); }
void emitMinus (std::ofstream &dest, int ct) { emitArith ("minus", -ct, dest); }
void emitLoadAndCast (std::string ptr, std::string val, std::string cast,
std::string type, std::ofstream &dest) {
dest << ptr << " = load sbyte** %ptrbox\n"
<< val << " = load sbyte* " << ptr << "\n"
<< cast << " = cast sbyte " << val << " to " << type << "\n";
}
// , becomes *p = getchar();
void emitComma(std::ofstream &dest, int ct) {
assert (ct == 1);
std::string ptr = gensym("commaptr"), read = gensym("commaread"),
cast = gensym("commacast");
dest << ptr << " = load sbyte** %ptrbox\n"
<< read << " = call int %getchar()\n"
<< cast << " = cast int " << read << " to sbyte\n"
<< "store sbyte " << cast << ", sbyte* " << ptr << "\n";
}
// . becomes putchar(*p);
void emitDot(std::ofstream &dest, int ct) {
assert (ct == 1);
std::string ptr = gensym("dotptr"), val = gensym("dotval"),
cast = gensym("dotcast");
emitLoadAndCast (ptr, val, cast, "int", dest);
dest << "call int %putchar(int " << cast << ")\n";
}
void emitPointerArith(std::string opname, int delta, std::ofstream &dest) {
std::string ptr = gensym(opname + "ptr"), result = gensym(opname + "result");
dest << ptr << " = load sbyte** %ptrbox\n"
<< result << " = getelementptr sbyte* " << ptr << ", int " << delta
<< "\n"
<< "store sbyte* " << result << ", sbyte** %ptrbox\n";
}
// < becomes --p; and > becomes ++p;
void emitLT(std::ofstream &dest, int ct) { emitPointerArith ("lt", -ct, dest); }
void emitGT(std::ofstream &dest, int ct) { emitPointerArith ("gt", +ct, dest); }
static std::vector<std::string> whileStack;
// [ becomes while (*p) {
void emitLeftBracket(std::ofstream &dest, int ct) {
assert (ct == 1);
std::string whileName = gensym ("While", false);
whileStack.push_back (whileName);
dest << "br label %testFor" << whileName << "\n"
<< "\ninside" << whileName << ":\n";
}
// ] becomes }
void emitRightBracket(std::ofstream &dest, int ct) {
assert (ct == 1);
std::string whileName = whileStack.back (),
ptr = gensym("bracketptr"),
val = gensym("bracketval"),
cast = gensym("bracketcast");
whileStack.pop_back ();
dest << "br label %testFor" << whileName << "\n"
<< "\ntestFor" << whileName << ":\n";
emitLoadAndCast (ptr, val, cast, "bool", dest);
dest << "br bool " << cast << ", label %inside" << whileName << ", "
<< "label %after" << whileName << "\n"
<< "\nafter" << whileName << ":\n";
}
typedef void (*FuncTy)(std::ofstream &, int);
static FuncTy table[256];
static bool multi[256];
void consume (int ch, int repeatCount, std::ofstream &dest) {
FuncTy func = table[ch];
if (!func)
return;
else if (multi[ch])
func (dest, repeatCount);
else
for (int i = 0; i < repeatCount; ++i)
func (dest, 1);
}
void initializeTable() {
memset (table, 0, 256);
memset (multi, 0, 256);
table[(int)'+'] = emitPlus; multi[(int)'+'] = true;
table[(int)'-'] = emitMinus; multi[(int)'-'] = true;
table[(int)','] = emitComma; multi[(int)','] = false;
table[(int)'.'] = emitDot; multi[(int)'.'] = false;
table[(int)'<'] = emitLT; multi[(int)'<'] = true;
table[(int)'>'] = emitGT; multi[(int)'>'] = true;
table[(int)'['] = emitLeftBracket; multi[(int)'['] = false;
table[(int)']'] = emitRightBracket; multi[(int)']'] = false;
}
int main (int argc, char **argv) {
if (argc != 3) {
std::cerr << "usage: " << argv[0] << " input-source output-llvm\n";
return 1;
}
char *sourceFileName = argv[1];
char *destFileName = argv[2];
std::ifstream src (sourceFileName);
if (!src.good()) {
std::cerr << sourceFileName << ": " << strerror(errno) << "\n";
return 1;
}
std::ofstream dest (destFileName);
if (!dest.good()) {
std::cerr << destFileName << ": " << strerror(errno) << "\n";
return 1;
}
emitDeclarations(dest);
emitMainFunctionProlog(dest);
initializeTable();
char ch, lastCh;
src >> lastCh;
int repeatCount = 1;
for (src >> ch; !src.eof (); src >> ch, ++repeatCount)
if (ch != lastCh) {
consume (lastCh, repeatCount, dest);
lastCh = ch;
repeatCount = 0;
}
consume (lastCh, repeatCount, dest);
emitMainFunctionEpilog(dest);
src.close();
dest.close();
return 0;
}
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