//===-- BrainF.cpp - BrainF compiler example ----------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===--------------------------------------------------------------------===//
//
// This class compiles the BrainF language into LLVM assembly.
//
// The BrainF language has 8 commands:
// Command Equivalent C Action
// ------- ------------ ------
// , *h=getchar(); Read a character from stdin, 255 on EOF
// . putchar(*h); Write a character to stdout
// - --*h; Decrement tape
// + ++*h; Increment tape
// < --h; Move head left
// > ++h; Move head right
// [ while(*h) { Start loop
// ] } End loop
//
//===--------------------------------------------------------------------===//
#include "BrainF.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include <iostream>
using namespace llvm;
//Set the constants for naming
const char *BrainF::tapereg = "tape";
const char *BrainF::headreg = "head";
const char *BrainF::label = "brainf";
const char *BrainF::testreg = "test";
Module *BrainF::parse(std::istream *in1, int mem, CompileFlags cf,
LLVMContext& Context) {
in = in1;
memtotal = mem;
comflag = cf;
header(Context);
readloop(nullptr, nullptr, nullptr, Context);
delete builder;
return module;
}
void BrainF::header(LLVMContext& C) {
module = new Module("BrainF", C);
//Function prototypes
//declare void @llvm.memset.p0i8.i32(i8 *, i8, i32, i32, i1)
Type *Tys[] = { Type::getInt8PtrTy(C), Type::getInt32Ty(C) };
Function *memset_func = Intrinsic::getDeclaration(module, Intrinsic::memset,
Tys);
//declare i32 @getchar()
getchar_func = cast<Function>(module->
getOrInsertFunction("getchar", IntegerType::getInt32Ty(C), NULL));
//declare i32 @putchar(i32)
putchar_func = cast<Function>(module->
getOrInsertFunction("putchar", IntegerType::getInt32Ty(C),
IntegerType::getInt32Ty(C), NULL));
//Function header
//define void @brainf()
brainf_func = cast<Function>(module->
getOrInsertFunction("brainf", Type::getVoidTy(C), NULL));
builder = new IRBuilder<>(BasicBlock::Create(C, label, brainf_func));
//%arr = malloc i8, i32 %d
ConstantInt *val_mem = ConstantInt::get(C, APInt(32, memtotal));
BasicBlock* BB = builder->GetInsertBlock();
Type* IntPtrTy = IntegerType::getInt32Ty(C);
Type* Int8Ty = IntegerType::getInt8Ty(C);
Constant* allocsize = ConstantExpr::getSizeOf(Int8Ty);
allocsize = ConstantExpr::getTruncOrBitCast(allocsize, IntPtrTy);
ptr_arr = CallInst::CreateMalloc(BB, IntPtrTy, Int8Ty, allocsize, val_mem,
nullptr, "arr");
BB->getInstList().push_back(cast<Instruction>(ptr_arr));
//call void @llvm.memset.p0i8.i32(i8 *%arr, i8 0, i32 %d, i32 1, i1 0)
{
Value *memset_params[] = {
ptr_arr,
ConstantInt::get(C, APInt(8, 0)),
val_mem,
ConstantInt::get(C, APInt(32, 1)),
ConstantInt::get(C, APInt(1, 0))
};
CallInst *memset_call = builder->
CreateCall(memset_func, memset_params);
memset_call->setTailCall(false);
}
//%arrmax = getelementptr i8 *%arr, i32 %d
if (comflag & flag_arraybounds) {
ptr_arrmax = builder->
CreateGEP(ptr_arr, ConstantInt::get(C, APInt(32, memtotal)), "arrmax");
}
//%head.%d = getelementptr i8 *%arr, i32 %d
curhead = builder->CreateGEP(ptr_arr,
ConstantInt::get(C, APInt(32, memtotal/2)),
headreg);
//Function footer
//brainf.end:
endbb = BasicBlock::Create(C, label, brainf_func);
//call free(i8 *%arr)
endbb->getInstList().push_back(CallInst::CreateFree(ptr_arr, endbb));
//ret void
ReturnInst::Create(C, endbb);
//Error block for array out of bounds
if (comflag & flag_arraybounds)
{
//@aberrormsg = internal constant [%d x i8] c"\00"
Constant *msg_0 =
ConstantDataArray::getString(C, "Error: The head has left the tape.",
true);
GlobalVariable *aberrormsg = new GlobalVariable(
*module,
msg_0->getType(),
true,
GlobalValue::InternalLinkage,
msg_0,
"aberrormsg");
//declare i32 @puts(i8 *)
Function *puts_func = cast<Function>(module->
getOrInsertFunction("puts", IntegerType::getInt32Ty(C),
PointerType::getUnqual(IntegerType::getInt8Ty(C)), NULL));
//brainf.aberror:
aberrorbb = BasicBlock::Create(C, label, brainf_func);
//call i32 @puts(i8 *getelementptr([%d x i8] *@aberrormsg, i32 0, i32 0))
{
Constant *zero_32 = Constant::getNullValue(IntegerType::getInt32Ty(C));
Constant *gep_params[] = {
zero_32,
zero_32
};
Constant *msgptr = ConstantExpr::
getGetElementPtr(aberrormsg->getValueType(), aberrormsg, gep_params);
Value *puts_params[] = {
msgptr
};
CallInst *puts_call =
CallInst::Create(puts_func,
puts_params,
"", aberrorbb);
puts_call->setTailCall(false);
}
//br label %brainf.end
BranchInst::Create(endbb, aberrorbb);
}
}
void BrainF::readloop(PHINode *phi, BasicBlock *oldbb, BasicBlock *testbb,
LLVMContext &C) {
Symbol cursym = SYM_NONE;
int curvalue = 0;
Symbol nextsym = SYM_NONE;
int nextvalue = 0;
char c;
int loop;
int direction;
while(cursym != SYM_EOF && cursym != SYM_ENDLOOP) {
// Write out commands
switch(cursym) {
case SYM_NONE:
// Do nothing
break;
case SYM_READ:
{
//%tape.%d = call i32 @getchar()
CallInst *getchar_call =
builder->CreateCall(getchar_func, {}, tapereg);
getchar_call->setTailCall(false);
Value *tape_0 = getchar_call;
//%tape.%d = trunc i32 %tape.%d to i8
Value *tape_1 = builder->
CreateTrunc(tape_0, IntegerType::getInt8Ty(C), tapereg);
//store i8 %tape.%d, i8 *%head.%d
builder->CreateStore(tape_1, curhead);
}
break;
case SYM_WRITE:
{
//%tape.%d = load i8 *%head.%d
LoadInst *tape_0 = builder->CreateLoad(curhead, tapereg);
//%tape.%d = sext i8 %tape.%d to i32
Value *tape_1 = builder->
CreateSExt(tape_0, IntegerType::getInt32Ty(C), tapereg);
//call i32 @putchar(i32 %tape.%d)
Value *putchar_params[] = {
tape_1
};
CallInst *putchar_call = builder->
CreateCall(putchar_func,
putchar_params);
putchar_call->setTailCall(false);
}
break;
case SYM_MOVE:
{
//%head.%d = getelementptr i8 *%head.%d, i32 %d
curhead = builder->
CreateGEP(curhead, ConstantInt::get(C, APInt(32, curvalue)),
headreg);
//Error block for array out of bounds
if (comflag & flag_arraybounds)
{
//%test.%d = icmp uge i8 *%head.%d, %arrmax
Value *test_0 = builder->
CreateICmpUGE(curhead, ptr_arrmax, testreg);
//%test.%d = icmp ult i8 *%head.%d, %arr
Value *test_1 = builder->
CreateICmpULT(curhead, ptr_arr, testreg);
//%test.%d = or i1 %test.%d, %test.%d
Value *test_2 = builder->
CreateOr(test_0, test_1, testreg);
//br i1 %test.%d, label %main.%d, label %main.%d
BasicBlock *nextbb = BasicBlock::Create(C, label, brainf_func);
builder->CreateCondBr(test_2, aberrorbb, nextbb);
//main.%d:
builder->SetInsertPoint(nextbb);
}
}
break;
case SYM_CHANGE:
{
//%tape.%d = load i8 *%head.%d
LoadInst *tape_0 = builder->CreateLoad(curhead, tapereg);
//%tape.%d = add i8 %tape.%d, %d
Value *tape_1 = builder->
CreateAdd(tape_0, ConstantInt::get(C, APInt(8, curvalue)), tapereg);
//store i8 %tape.%d, i8 *%head.%d\n"
builder->CreateStore(tape_1, curhead);
}
break;
case SYM_LOOP:
{
//br label %main.%d
BasicBlock *testbb = BasicBlock::Create(C, label, brainf_func);
builder->CreateBr(testbb);
//main.%d:
BasicBlock *bb_0 = builder->GetInsertBlock();
BasicBlock *bb_1 = BasicBlock::Create(C, label, brainf_func);
builder->SetInsertPoint(bb_1);
// Make part of PHI instruction now, wait until end of loop to finish
PHINode *phi_0 =
PHINode::Create(PointerType::getUnqual(IntegerType::getInt8Ty(C)),
2, headreg, testbb);
phi_0->addIncoming(curhead, bb_0);
curhead = phi_0;
readloop(phi_0, bb_1, testbb, C);
}
break;
default:
std::cerr << "Error: Unknown symbol.\n";
abort();
break;
}
cursym = nextsym;
curvalue = nextvalue;
nextsym = SYM_NONE;
// Reading stdin loop
loop = (cursym == SYM_NONE)
|| (cursym == SYM_MOVE)
|| (cursym == SYM_CHANGE);
while(loop) {
*in>>c;
if (in->eof()) {
if (cursym == SYM_NONE) {
cursym = SYM_EOF;
} else {
nextsym = SYM_EOF;
}
loop = 0;
} else {
direction = 1;
switch(c) {
case '-':
direction = -1;
// Fall through
case '+':
if (cursym == SYM_CHANGE) {
curvalue += direction;
// loop = 1
} else {
if (cursym == SYM_NONE) {
cursym = SYM_CHANGE;
curvalue = direction;
// loop = 1
} else {
nextsym = SYM_CHANGE;
nextvalue = direction;
loop = 0;
}
}
break;
case '<':
direction = -1;
// Fall through
case '>':
if (cursym == SYM_MOVE) {
curvalue += direction;
// loop = 1
} else {
if (cursym == SYM_NONE) {
cursym = SYM_MOVE;
curvalue = direction;
// loop = 1
} else {
nextsym = SYM_MOVE;
nextvalue = direction;
loop = 0;
}
}
break;
case ',':
if (cursym == SYM_NONE) {
cursym = SYM_READ;
} else {
nextsym = SYM_READ;
}
loop = 0;
break;
case '.':
if (cursym == SYM_NONE) {
cursym = SYM_WRITE;
} else {
nextsym = SYM_WRITE;
}
loop = 0;
break;
case '[':
if (cursym == SYM_NONE) {
cursym = SYM_LOOP;
} else {
nextsym = SYM_LOOP;
}
loop = 0;
break;
case ']':
if (cursym == SYM_NONE) {
cursym = SYM_ENDLOOP;
} else {
nextsym = SYM_ENDLOOP;
}
loop = 0;
break;
// Ignore other characters
default:
break;
}
}
}
}
if (cursym == SYM_ENDLOOP) {
if (!phi) {
std::cerr << "Error: Extra ']'\n";
abort();
}
// Write loop test
{
//br label %main.%d
builder->CreateBr(testbb);
//main.%d:
//%head.%d = phi i8 *[%head.%d, %main.%d], [%head.%d, %main.%d]
//Finish phi made at beginning of loop
phi->addIncoming(curhead, builder->GetInsertBlock());
Value *head_0 = phi;
//%tape.%d = load i8 *%head.%d
LoadInst *tape_0 = new LoadInst(head_0, tapereg, testbb);
//%test.%d = icmp eq i8 %tape.%d, 0
ICmpInst *test_0 = new ICmpInst(*testbb, ICmpInst::ICMP_EQ, tape_0,
ConstantInt::get(C, APInt(8, 0)), testreg);
//br i1 %test.%d, label %main.%d, label %main.%d
BasicBlock *bb_0 = BasicBlock::Create(C, label, brainf_func);
BranchInst::Create(bb_0, oldbb, test_0, testbb);
//main.%d:
builder->SetInsertPoint(bb_0);
//%head.%d = phi i8 *[%head.%d, %main.%d]
PHINode *phi_1 = builder->
CreatePHI(PointerType::getUnqual(IntegerType::getInt8Ty(C)), 1,
headreg);
phi_1->addIncoming(head_0, testbb);
curhead = phi_1;
}
return;
}
//End of the program, so go to return block
builder->CreateBr(endbb);
if (phi) {
std::cerr << "Error: Missing ']'\n";
abort();
}
}