Instantly share code, notes, and snippets.

Embed
What would you like to do?
llvm-brainfuck: Simple operations
#include <cstdio>
#include <llvm/LLVMContext.h>
#include <llvm/Module.h>
#include <llvm/Support/IRBuilder.h>
#include <llvm/Support/raw_ostream.h>
using namespace llvm;
static const uint64_t DATA_SIZE = 30000;
static const char *DATA_NAME = "data";
static const char *PTR_NAME = "ptr";
int main() {
// LLVM context.
LLVMContext &Context = getGlobalContext();
Module MainModule("brainfuck program", Context);
IRBuilder<> Builder(Context);
// Some useful constants.
const IntegerType *CellType = Type::getInt8Ty(Context);
Constant *One = ConstantInt::get(CellType, 1);
// Global data for a brainfuck program.
ArrayType *DataType = ArrayType::get(CellType, DATA_SIZE);
GlobalVariable *Data = new GlobalVariable(
MainModule, DataType, false /* constant */,
GlobalVariable::InternalLinkage, Constant::getNullValue(DataType),
DATA_NAME);
Value *DataPtr = Builder.CreateConstInBoundsGEP2_32(Data, 0, 0, PTR_NAME);
(void) DataPtr; // unused
// Main function definition.
FunctionType *MainFunctionType = FunctionType::get(
Type::getVoidTy(Context) /* return type */,
std::vector<const Type *>() /* argument types */,
false /* var args */);
Function *MainFunction = Function::Create(MainFunctionType,
Function::ExternalLinkage, "brainfuck_main", &MainModule);
BasicBlock *MainBlock = BasicBlock::Create(Context, "entry", MainFunction);
Builder.SetInsertPoint(MainBlock);
// Code generation.
int c;
Value *Value;
while ((c = getchar()) != EOF) {
switch (c) {
case '>':
DataPtr = Builder.CreateConstGEP1_32(DataPtr, 1, PTR_NAME);
break;
case '<':
DataPtr = Builder.CreateConstGEP1_32(DataPtr, -1, PTR_NAME);
break;
case '+':
Value = Builder.CreateLoad(DataPtr);
Value = Builder.CreateAdd(Value, One);
Builder.CreateStore(Value, DataPtr);
break;
case '-':
Value = Builder.CreateLoad(DataPtr);
Value = Builder.CreateSub(Value, One);
Builder.CreateStore(Value, DataPtr);
break;
}
}
// Finish off brainfuck_main and dump.
Builder.CreateRetVoid();
MainModule.print(outs(), NULL /* assembly annotation writer */);
}
PROGRAM := llvm-brainfuck
OBJECTS := main.o
CXX := clang++
CXXFLAGS := $(shell llvm-config --cppflags) -Wall -Werror -pedantic
LDFLAGS := $(shell llvm-config --ldflags --libs core)
all: $(PROGRAM) $(SHIM)
$(PROGRAM): $(OBJECTS)
$(CXX) -o $@ $^ $(LDFLAGS)
clean:
rm -f $(PROGRAM) $(OBJECTS)
.PHONY: clean all
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment