source_filename = "while_test.sy"
target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

@b = dso_local global i32 0, align 4
@a = dso_local global i32 0, align 4

define dso_local i32 @main() {
  store i32 0, i32* @b, align 4
  store i32 3, i32* @a, align 4   ; b, a分别赋给0, 3
  br label %1 ; 跳转到标签2处

1:
  %2 = load i32, i32* @a, align 4
  %3 = icmp sgt i32 %2, 0
  br i1 %3, label %4, label %10   ; 判断a是否大于0，大于则进入循环

4:
  %5 = load i32, i32* @b, align 4
  %6 = load i32, i32* @a, align 4
  %7 = add i32 %5, %6
  store i32 %7, i32* @b, align 4
  %8 = load i32, i32* @a, align 4
  %9 = sub i32 %8, 1
  store i32 %9, i32* @a, align 4 ; 进入循环，执行b = b+a; a = a-1;
  br label %1 ; 跳转循环开头

10:
  %11 = load i32, i32* @b, align 4
  ret i32 %11 ; 加载%b并返回
}