llvm
Library for interacting with LLVM IR in pure Go.
Introduction
Installation
go get -u github.com/llir/llvm/...
Versions
Map between llir/llvm tagged releases and LLVM release versions.
- llir/llvm v0.3.2: LLVM 10.0
- llir/llvm v0.3.0: LLVM 9.0
Users
- decomp: LLVM IR to Go decompiler by @decomp.
- geode: Geode to LLVM IR compiler by @nickwanninger.
- leaven: LLVM IR to Go decompiler by @andybalholm.
- slate: Slate to LLVM IR compiler by @nektro.
- tre: Go to LLVM IR compiler by @zegl.
- uc: µC to LLVM IR compiler by @sangisos and @mewmew.
Usage
Input example - Parse LLVM IR assembly
// This example parses an LLVM IR assembly file and pretty-prints the data types
// of the parsed module to standard output.
package main
import (
"log"
"github.com/kr/pretty"
"github.com/llir/llvm/asm"
)
func main() {
// Parse the LLVM IR assembly file `foo.ll`.
m, err := asm.ParseFile("foo.ll")
if err != nil {
log.Fatalf("%+v", err)
}
// Pretty-print the data types of the parsed LLVM IR module.
pretty.Println(m)
}
Output example - Produce LLVM IR assembly
// This example produces LLVM IR code equivalent to the following C code, which
// implements a pseudo-random number generator.
//
// int abs(int x);
//
// int seed = 0;
//
// // ref: https://en.wikipedia.org/wiki/Linear_congruential_generator
// // a = 0x15A4E35
// // c = 1
// int rand(void) {
// seed = seed*0x15A4E35 + 1;
// return abs(seed);
// }
package main
import (
"fmt"
"github.com/llir/llvm/ir"
"github.com/llir/llvm/ir/constant"
"github.com/llir/llvm/ir/types"
)
func main() {
// Create convenience types and constants.
i32 := types.I32
zero := constant.NewInt(i32, 0)
a := constant.NewInt(i32, 0x15A4E35) // multiplier of the PRNG.
c := constant.NewInt(i32, 1) // increment of the PRNG.
// Create a new LLVM IR module.
m := ir.NewModule()
// Create an external function declaration and append it to the module.
//
// int abs(int x);
abs := m.NewFunc("abs", i32, ir.NewParam("x", i32))
// Create a global variable definition and append it to the module.
//
// int seed = 0;
seed := m.NewGlobalDef("seed", zero)
// Create a function definition and append it to the module.
//
// int rand(void) { ... }
rand := m.NewFunc("rand", i32)
// Create an unnamed entry basic block and append it to the `rand` function.
entry := rand.NewBlock("")
// Create instructions and append them to the entry basic block.
tmp1 := entry.NewLoad(i32, seed)
tmp2 := entry.NewMul(tmp1, a)
tmp3 := entry.NewAdd(tmp2, c)
entry.NewStore(tmp3, seed)
tmp4 := entry.NewCall(abs, tmp3)
entry.NewRet(tmp4)
// Print the LLVM IR assembly of the module.
fmt.Println(m)
}
Analysis example - Process LLVM IR
// This example program analyses an LLVM IR module to produce a callgraph in
// Graphviz DOT format.
package main
import (
"fmt"
"strings"
"github.com/llir/llvm/asm"
"github.com/llir/llvm/ir"
)
func main() {
// Parse LLVM IR assembly file.
m, err := asm.ParseFile("foo.ll")
if err != nil {
panic(err)
}
// Produce callgraph of module.
callgraph := genCallgraph(m)
// Output callgraph in Graphviz DOT format.
fmt.Println(callgraph)
}
// genCallgraph returns the callgraph in Graphviz DOT format of the given LLVM
// IR module.
func genCallgraph(m *ir.Module) string {
buf := &strings.Builder{}
buf.WriteString("digraph {\n")
// For each function of the module.
for _, f := range m.Funcs {
// Add caller node.
caller := f.Ident()
fmt.Fprintf(buf, "\t%q\n", caller)
// For each basic block of the function.
for _, block := range f.Blocks {
// For each non-branching instruction of the basic block.
for _, inst := range block.Insts {
// Type switch on instruction to find call instructions.
switch inst := inst.(type) {
case *ir.InstCall:
callee := inst.Callee.Ident()
// Add edges from caller to callee.
fmt.Fprintf(buf, "\t%q -> %q\n", caller, callee)
}
}
// Terminator of basic block.
switch term := block.Term.(type) {
case *ir.TermRet:
// do something.
_ = term
}
}
}
buf.WriteString("}")
return buf.String()
}
License
The llir/llvm project is dual-licensed to the public domain and under a zero-clause BSD license. You may choose either license to govern your use of llir/llvm.
