Contains bugs fixes and improvements upon JuliaComputingOSS/llvm-cbe
Takes LLVM SSA intermediate representation and elevates it back up to C code
For example, you can start off with a .c file:
#include <CoreFoundation/CoreFoundation.h>
void macMessageBox(const char *title, const char *text)
{
SInt32 nRes = 0;
CFUserNotificationRef pDlg = NULL;
const void *keys[] = {kCFUserNotificationAlertHeaderKey, kCFUserNotificationAlertMessageKey};
CFStringRef cfTitle = CFStringCreateWithCString(NULL, title, kCFStringEncodingWindowsLatin1);
CFStringRef cfText = CFStringCreateWithCString(NULL, text, kCFStringEncodingWindowsLatin1);
const void *vals[] = {
cfTitle, cfText
};
CFDictionaryRef dict = CFDictionaryCreate(0, keys, vals, sizeof(keys) / sizeof(*keys), &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
pDlg = CFUserNotificationCreate(kCFAllocatorDefault, 0, kCFUserNotificationStopAlertLevel, &nRes, dict);
CFRelease(cfTitle);
CFRelease(cfText);
CFRelease(pDlg);
}
int main(int argc, const char** argv)
{
for(int i = 0; i != 3; i++){
const char *something = argv[0];
macMessageBox(something, "Whatever this is");
}
return 0;
}
Then generate the low level SAA intermediate representation for it with clang:
; ModuleID = 'alert.c'
source_filename = "alert.c"
target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
target triple = "arm64-apple-macosx11.0.0"
%struct.__CFString = type opaque
%struct.CFDictionaryKeyCallBacks = type { i64, i8* (%struct.__CFAllocator*, i8*)*, void (%struct.__CFAllocator*, i8*)*, %struct.__CFString* (i8*)*, i8 (i8*, i8*)*, i64 (i8*)* }
%struct.__CFAllocator = type opaque
%struct.CFDictionaryValueCallBacks = type { i64, i8* (%struct.__CFAllocator*, i8*)*, void (%struct.__CFAllocator*, i8*)*, %struct.__CFString* (i8*)*, i8 (i8*, i8*)* }
%struct.__CFUserNotification = type opaque
%struct.__CFDictionary = type opaque
@kCFUserNotificationAlertHeaderKey = external constant %struct.__CFString*, align 8
@kCFUserNotificationAlertMessageKey = external constant %struct.__CFString*, align 8
@kCFTypeDictionaryKeyCallBacks = external constant %struct.CFDictionaryKeyCallBacks, align 8
@kCFTypeDictionaryValueCallBacks = external constant %struct.CFDictionaryValueCallBacks, align 8
@kCFAllocatorDefault = external constant %struct.__CFAllocator*, align 8
@.str = private unnamed_addr constant [17 x i8] c"Whatever this is\00", align 1
; Function Attrs: noinline nounwind optnone ssp uwtable
define void @macMessageBox(i8* %0, i8* %1) #0 {
%3 = alloca i8*, align 8
%4 = alloca i8*, align 8
%5 = alloca i32, align 4
%6 = alloca %struct.__CFUserNotification*, align 8
%7 = alloca [2 x i8*], align 8
%8 = alloca %struct.__CFString*, align 8
%9 = alloca %struct.__CFString*, align 8
%10 = alloca [2 x i8*], align 8
%11 = alloca %struct.__CFDictionary*, align 8
store i8* %0, i8** %3, align 8
store i8* %1, i8** %4, align 8
store i32 0, i32* %5, align 4
store %struct.__CFUserNotification* null, %struct.__CFUserNotification** %6, align 8
%12 = getelementptr inbounds [2 x i8*], [2 x i8*]* %7, i64 0, i64 0
%13 = load %struct.__CFString*, %struct.__CFString** @kCFUserNotificationAlertHeaderKey, align 8
%14 = bitcast %struct.__CFString* %13 to i8*
store i8* %14, i8** %12, align 8
%15 = getelementptr inbounds i8*, i8** %12, i64 1
%16 = load %struct.__CFString*, %struct.__CFString** @kCFUserNotificationAlertMessageKey, align 8
%17 = bitcast %struct.__CFString* %16 to i8*
store i8* %17, i8** %15, align 8
%18 = load i8*, i8** %3, align 8
%19 = call %struct.__CFString* @CFStringCreateWithCString(%struct.__CFAllocator* null, i8* %18, i32 1280)
store %struct.__CFString* %19, %struct.__CFString** %8, align 8
%20 = load i8*, i8** %4, align 8
%21 = call %struct.__CFString* @CFStringCreateWithCString(%struct.__CFAllocator* null, i8* %20, i32 1280)
store %struct.__CFString* %21, %struct.__CFString** %9, align 8
%22 = getelementptr inbounds [2 x i8*], [2 x i8*]* %10, i64 0, i64 0
%23 = load %struct.__CFString*, %struct.__CFString** %8, align 8
%24 = bitcast %struct.__CFString* %23 to i8*
store i8* %24, i8** %22, align 8
%25 = getelementptr inbounds i8*, i8** %22, i64 1
%26 = load %struct.__CFString*, %struct.__CFString** %9, align 8
%27 = bitcast %struct.__CFString* %26 to i8*
store i8* %27, i8** %25, align 8
%28 = getelementptr inbounds [2 x i8*], [2 x i8*]* %7, i64 0, i64 0
%29 = getelementptr inbounds [2 x i8*], [2 x i8*]* %10, i64 0, i64 0
%30 = call %struct.__CFDictionary* @CFDictionaryCreate(%struct.__CFAllocator* null, i8** %28, i8** %29, i64 2, %struct.CFDictionaryKeyCallBacks* @kCFTypeDictionaryKeyCallBacks, %struct.CFDictionaryValueCallBacks* @kCFTypeDictionaryValueCallBacks)
store %struct.__CFDictionary* %30, %struct.__CFDictionary** %11, align 8
%31 = load %struct.__CFAllocator*, %struct.__CFAllocator** @kCFAllocatorDefault, align 8
%32 = load %struct.__CFDictionary*, %struct.__CFDictionary** %11, align 8
%33 = call %struct.__CFUserNotification* @CFUserNotificationCreate(%struct.__CFAllocator* %31, double 0.000000e+00, i64 0, i32* %5, %struct.__CFDictionary* %32)
store %struct.__CFUserNotification* %33, %struct.__CFUserNotification** %6, align 8
%34 = load %struct.__CFString*, %struct.__CFString** %8, align 8
%35 = bitcast %struct.__CFString* %34 to i8*
call void @CFRelease(i8* %35)
%36 = load %struct.__CFString*, %struct.__CFString** %9, align 8
%37 = bitcast %struct.__CFString* %36 to i8*
call void @CFRelease(i8* %37)
%38 = load %struct.__CFUserNotification*, %struct.__CFUserNotification** %6, align 8
%39 = bitcast %struct.__CFUserNotification* %38 to i8*
call void @CFRelease(i8* %39)
ret void
}
declare %struct.__CFString* @CFStringCreateWithCString(%struct.__CFAllocator*, i8*, i32) #1
declare %struct.__CFDictionary* @CFDictionaryCreate(%struct.__CFAllocator*, i8**, i8**, i64, %struct.CFDictionaryKeyCallBacks*, %struct.CFDictionaryValueCallBacks*) #1
declare %struct.__CFUserNotification* @CFUserNotificationCreate(%struct.__CFAllocator*, double, i64, i32*, %struct.__CFDictionary*) #1
declare void @CFRelease(i8*) #1
; Function Attrs: noinline nounwind optnone ssp uwtable
define i32 @main(i32 %0, i8** %1) #0 {
%3 = alloca i32, align 4
%4 = alloca i32, align 4
%5 = alloca i8**, align 8
%6 = alloca i32, align 4
%7 = alloca i8*, align 8
store i32 0, i32* %3, align 4
store i32 %0, i32* %4, align 4
store i8** %1, i8*** %5, align 8
store i32 0, i32* %6, align 4
br label %8
8: ; preds = %16, %2
%9 = load i32, i32* %6, align 4
%10 = icmp ne i32 %9, 3
br i1 %10, label %11, label %19
11: ; preds = %8
%12 = load i8**, i8*** %5, align 8
%13 = getelementptr inbounds i8*, i8** %12, i64 0
%14 = load i8*, i8** %13, align 8
store i8* %14, i8** %7, align 8
%15 = load i8*, i8** %7, align 8
call void @macMessageBox(i8* %15, i8* getelementptr inbounds ([17 x i8], [17 x i8]* @.str, i64 0, i64 0))
br label %16
16: ; preds = %11
%17 = load i32, i32* %6, align 4
%18 = add nsw i32 %17, 1
store i32 %18, i32* %6, align 4
br label %8
19: ; preds = %8
ret i32 0
}
attributes #0 = { noinline nounwind optnone ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="non-leaf" "less-precise-fpmad"="false" "min-legal-vector-width"="0" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "probe-stack"="__chkstk_darwin" "stack-protector-buffer-size"="8" "target-cpu"="apple-a12" "target-features"="+aes,+crc,+crypto,+fp-armv8,+fullfp16,+lse,+neon,+ras,+rcpc,+rdm,+sha2,+v8.3a,+zcm,+zcz" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "frame-pointer"="non-leaf" "less-precise-fpmad"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="true" "probe-stack"="__chkstk_darwin" "stack-protector-buffer-size"="8" "target-cpu"="apple-a12" "target-features"="+aes,+crc,+crypto,+fp-armv8,+fullfp16,+lse,+neon,+ras,+rcpc,+rdm,+sha2,+v8.3a,+zcm,+zcz" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.module.flags = !{!0, !1, !2}
!llvm.ident = !{!3}
!0 = !{i32 2, !"SDK Version", [2 x i32] [i32 11, i32 3]}
!1 = !{i32 1, !"wchar_size", i32 4}
!2 = !{i32 7, !"PIC Level", i32 2}
!3 = !{!"Apple clang version 12.0.5 (clang-1205.0.22.11)"}
And then by using llvm-cbe you can elevate it back up to non-human-readable C code:
/* Provide Declarations */
#include <stdint.h>
#ifndef __cplusplus
typedef unsigned char bool;
#endif
#ifndef _MSC_VER
#define __forceinline __attribute__((always_inline)) inline
#endif
#if defined(__GNUC__)
#define __ATTRIBUTELIST__(x) __attribute__(x)
#else
#define __ATTRIBUTELIST__(x)
#endif
#ifdef _MSC_VER /* Can only support "linkonce" vars with GCC */
#define __attribute__(X)
#endif
/* Global Declarations */
/* Types Declarations */
struct l_struct_struct_OC_CFDictionaryKeyCallBacks;
struct l_struct_struct_OC_CFDictionaryValueCallBacks;
/* Function definitions */
typedef void l_fptr_2(void*, uint8_t*);
typedef uint64_t l_fptr_5(uint8_t*);
typedef uint8_t* l_fptr_1(void*, uint8_t*);
typedef void* l_fptr_3(uint8_t*);
typedef uint8_t l_fptr_4(uint8_t*, uint8_t*);
/* Types Definitions */
struct l_struct_struct_OC_CFDictionaryKeyCallBacks {
uint64_t field0;
l_fptr_1* field1;
l_fptr_2* field2;
l_fptr_3* field3;
l_fptr_4* field4;
l_fptr_5* field5;
};
struct l_struct_struct_OC_CFDictionaryValueCallBacks {
uint64_t field0;
l_fptr_1* field1;
l_fptr_2* field2;
l_fptr_3* field3;
l_fptr_4* field4;
};
struct l_array_17_uint8_t {
uint8_t array[17];
};
struct l_array_2_uint8_t_KC_ {
uint8_t* array[2];
};
/* External Global Variable Declarations */
extern void* kCFUserNotificationAlertHeaderKey;
extern void* kCFUserNotificationAlertMessageKey;
extern struct l_struct_struct_OC_CFDictionaryKeyCallBacks kCFTypeDictionaryKeyCallBacks;
extern struct l_struct_struct_OC_CFDictionaryValueCallBacks kCFTypeDictionaryValueCallBacks;
extern void* kCFAllocatorDefault;
/* Function Declarations */
void macMessageBox(uint8_t*, uint8_t*) __ATTRIBUTELIST__((noinline, nothrow, stack_protect));
void* CFStringCreateWithCString(void*, uint8_t*, uint32_t);
void* CFDictionaryCreate(void*, uint8_t**, uint8_t**, uint64_t, struct l_struct_struct_OC_CFDictionaryKeyCallBacks*, struct l_struct_struct_OC_CFDictionaryValueCallBacks*);
void* CFUserNotificationCreate(void*, double, uint64_t, uint32_t*, void*);
void CFRelease(uint8_t*);
int main(int, char **) __ATTRIBUTELIST__((noinline, nothrow, stack_protect));
/* Global Variable Definitions and Initialization */
static struct l_array_17_uint8_t _OC_str = { "Whatever this is" };
/* LLVM Intrinsic Builtin Function Bodies */
static __forceinline uint32_t llvm_add_u32(uint32_t a, uint32_t b) {
uint32_t r = a + b;
return r;
}
/* Function Bodies */
void macMessageBox(uint8_t* _1, uint8_t* _2) {
uint8_t* _3; /* Address-exposed local */
uint8_t* _4; /* Address-exposed local */
uint32_t _5; /* Address-exposed local */
void* _6; /* Address-exposed local */
struct l_array_2_uint8_t_KC_ _7; /* Address-exposed local */
void* _8; /* Address-exposed local */
void* _9; /* Address-exposed local */
struct l_array_2_uint8_t_KC_ _10; /* Address-exposed local */
void* _11; /* Address-exposed local */
uint8_t** _12;
void* _13;
void* _14;
uint8_t* _15;
void* _16;
uint8_t* _17;
void* _18;
uint8_t** _19;
void* _20;
void* _21;
void* _22;
void* _23;
void* _24;
void* _25;
void* _26;
void* _27;
void* _28;
_3 = _1;
_4 = _2;
_5 = 0;
_6 = ((void*)/*NULL*/0);
_12 = (&_7.array[((int64_t)0)]);
_13 = kCFUserNotificationAlertHeaderKey;
*_12 = (((uint8_t*)_13));
_14 = kCFUserNotificationAlertMessageKey;
*((&_12[((int64_t)1)])) = (((uint8_t*)_14));
_15 = _3;
_16 = CFStringCreateWithCString(((void*)/*NULL*/0), _15, 1280);
_8 = _16;
_17 = _4;
_18 = CFStringCreateWithCString(((void*)/*NULL*/0), _17, 1280);
_9 = _18;
_19 = (&_10.array[((int64_t)0)]);
_20 = _8;
*_19 = (((uint8_t*)_20));
_21 = _9;
*((&_19[((int64_t)1)])) = (((uint8_t*)_21));
_22 = CFDictionaryCreate(((void*)/*NULL*/0), ((&_7.array[((int64_t)0)])), ((&_10.array[((int64_t)0)])), 2, (&kCFTypeDictionaryKeyCallBacks), (&kCFTypeDictionaryValueCallBacks));
_11 = _22;
_23 = kCFAllocatorDefault;
_24 = _11;
_25 = CFUserNotificationCreate(_23, 0, 0, (&_5), _24);
_6 = _25;
_26 = _8;
CFRelease((((uint8_t*)_26)));
_27 = _9;
CFRelease((((uint8_t*)_27)));
_28 = _6;
CFRelease((((uint8_t*)_28)));
}
int main(int argc, char ** argv) {
uint32_t _29 = (uint32_t)argc;
uint8_t** _30 = (uint8_t**)argv;
uint32_t _31; /* Address-exposed local */
uint32_t _32; /* Address-exposed local */
uint8_t** _33; /* Address-exposed local */
uint32_t _34; /* Address-exposed local */
uint8_t* _35; /* Address-exposed local */
uint32_t _36;
uint8_t** _37;
uint8_t* _38;
uint8_t* _39;
uint32_t _40;
_31 = 0;
_32 = _29;
_33 = _30;
_34 = 0;
goto _41;
do { /* Syntactic loop '' to make GCC happy */
_41:
_36 = _34;
if ((_36 != 3u)) {
goto _42;
} else {
goto _43;
}
_42:
_37 = _33;
_38 = *((&(*_37)));
_35 = _38;
_39 = _35;
macMessageBox(_39, ((&_OC_str.array[((int64_t)0)])));
goto _44;
_44:
_40 = _34;
_34 = (llvm_add_u32(_40, 1));
goto _41;
} while (1); /* end of syntactic loop '' */
_43:
return 0;
}
And then compile and link it as if it was the original .c file.
This LLVM C backend has been resurrected by Julia Computing with various improvements.
This version of the LLVM C backend works with LLVM 10.0, and has preliminary support for LLVM 11.0.
On macOS, use pkgsrc and run the following commands:
pkgin in llvm clang
On CentOS, install the llvm-devel package:
dnf install llvm-devel clang
On Debian and derivatives, install the llvm-dev package via:
apt install llvm-dev clang
Note: to convert C to LLVM IR to run the tests, you will also need a C compiler using the LLVM infrastructure, such as clang.
The first step is to compile LLVM on your machine (this assumes an in-tree build, but out-of-tree will also work):
git clone https://github.com/llvm/llvm-project.git
cd llvm-project
git checkout release/8.x
mkdir llvm/build
cd llvm/build
cmake ..
make
To run tests, you need to build lli.
Now you can download and compile llvm-cbe.
If you built LLVM yourself, put it in the same folder you built LLVM in:
cd $HOME/llvm-project/llvm/projects
git clone https://github.com/JuliaComputing/llvm-cbe
cd ../build
cmake -S ..
make llvm-cbe
If you used your distribution's package, put it wherever you feel like:
git clone https://github.com/JuliaComputing/llvm-cbe
cd llvm-cbe && mkdir build && cd build
cmake -S ..
make llvm-cbe
If llvm-cbe compiles, you should be able to run it with the following commands.
$ cd $HOME/llvm-project/llvm/projects/llvm-cbe/test/selectionsort
$ ls
main.c
$ clang -S -emit-llvm -g main.c
$ ls
main.c main.ll
$ $(HOME)/llvm/build/bin/llvm-cbe main.ll
You can find options to configure the C backend's output with llvm-cbe --help.
Look for options beginning with --cbe-.
$ gcc -o main.cbe main.cbe.c
$ ls
main.c main.cbe main.cbe.c main.ll
$ ./main.cbe
Unit tests:
$ cd $HOME/llvm-project/llvm/build
$ make CBEUnitTests && projects/llvm-cbe/unittests/CWriterTestNote that you need to have passed -DLLVM_INCLUDE_TESTS=1 to cmake if you used
your distribution's LLVM package. You also will need to install gtest (on Debian
derivatives: apt install libgtest-dev).
Other tests:
First, compile llvm-cbe, and install pytest (e.g. pip install pytest). Then:
$ cd $HOME/llvm-project/llvm/projects/llvm-cbe
$ pytestYou might have to adjust the llvm-cbe and lli paths in that configuration.
If you want the tests to run faster, installing pytest-xdist will allow you to run the test suite in parallel, e.g. pytest -n 4 if you want to use 4 cores.