使用clang将C/C++代码编译成LLVM的中间代码(LLVM ir bitcode)，并反汇编LLVM bitcode

test.c文件内容如下：

#include
int main(void){
    printf("hello world!\n");
    return 0;
}

clang是使用LLVM最为后端，所以支持编译成LLVM的字节码

clang -emit-llvm -o test.bc -c test.c

将LLVM bitcode 进一步编译为汇编：

clang -o test test.bc

LLVM-DIS命令是LLVM反汇编。它可以一个LLVM bitcode文件并将其转换为人类可读的LLVM汇编语言。
反编译LLVM 字节码：

zhang@debian:~$ llvm-dis test.bc -o -
; ModuleID = 'test.bc'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

@.str = private unnamed_addr constant [14 x i8] c"hello world!\0A\00", align 1

; Function Attrs: nounwind uwtable
define i32 @main() #0 {
  %1 = alloca i32, align 4
  store i32 0, i32* %1, align 4
  %2 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([14 x i8], [14 x i8]* @.str, i32 0, i32 0))
  ret i32 0
}

declare i32 @printf(i8*, ...) #1

attributes #0 = { nounwind uwtable "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2" "unsafe-fp-math"="false" "use-soft-float"="false" }

!llvm.ident = !{!0}

!0 = !{!"clang version 3.8.1-24 (tags/RELEASE_381/final)"}

参考文章：c - How to make clang compile to llvm IR - Stack Overflow