Leaven: Compile LLVM IR to Go
Leaven translates LLVM intermediate representation to Go. In theory, it should be able to transpile any language that has an LLVM-based compiler to Go. But so far Iβve only used it for C.
Each LLVM instruction is translated to an equivalent statement in Go. This produces very verbose code; if you are looking for a tool that will convert a C codebase into maintainable Go, Leaven isnβt it.
But it does allow you to call C code from Go without using CGo. And I am hoping that it can produce a working Go translation of a program, which will be a good starting point for incrementally re-translating it (probably by hand) into idiomatic Go.
Warning
This software is incomplete and experimental. It does not support nearly all LLVM instructions.
The transpiler at github.com/andybalholm/c2go produces much better results (but it is not as automatic).
Usage Example
(Translating strcmp from musl libc.)
$ cat strcmp.c
#include <string.h>
int strcmp(const char *l, const char *r)
{
for (; *l==*r && *l; l++, r++);
return *(unsigned char *)l - *(unsigned char *)r;
}
$ clang -S -emit-llvm -fno-discard-value-names strcmp.c
$ leaven strcmp.ll
$ goimports -w strcmp.go
$ cat strcmp.go
package main
import "unsafe"
func strcmp(l *byte, r *byte) int32 {
var l_addr, r_addr **byte
var v0, v2, v4, v7, incdec_ptr, v8, incdec_ptr4, v9, v11 *byte
var cmp, tobool, v6 bool
var v1, v3, v5, v10, v12 byte
var conv, conv1, conv3, conv5, conv6, sub int32
_, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _, _ = l_addr, r_addr, v0, v1, conv, v2, v3, conv1, cmp, v4, v5, conv3, tobool, v6, v7, incdec_ptr, v8, incdec_ptr4, v9, v10, conv5, v11, v12, conv6, sub
l_addr = new(*byte)
r_addr = new(*byte)
*l_addr = l
*r_addr = r
goto for_cond
for_cond:
v0 = *l_addr
v1 = *v0
conv = int32(int8(v1))
v2 = *r_addr
v3 = *v2
conv1 = int32(int8(v3))
cmp = conv == conv1
if cmp {
goto land_rhs
} else {
v6 = false
goto land_end
}
land_rhs:
v4 = *l_addr
v5 = *v4
conv3 = int32(int8(v5))
tobool = conv3 != 0
v6 = tobool
goto land_end
land_end:
if v6 {
goto for_body
} else {
goto for_end
}
for_body:
goto for_inc
for_inc:
v7 = *l_addr
incdec_ptr = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(v7)) + 1*unsafe.Sizeof(*(*byte)(nil))))
*l_addr = incdec_ptr
v8 = *r_addr
incdec_ptr4 = (*byte)(unsafe.Pointer(uintptr(unsafe.Pointer(v8)) + 1*unsafe.Sizeof(*(*byte)(nil))))
*r_addr = incdec_ptr4
goto for_cond
for_end:
v9 = *l_addr
v10 = *v9
conv5 = int32(uint32(v10))
v11 = *r_addr
v12 = *v11
conv6 = int32(uint32(v12))
sub = conv5 - conv6
return sub
}