作为标题，为什么main（）有变量'retval'但没有使用？而本地func test（）没有任何名为'retval'的变量。
“hello. c”

#include <stdio.h>

int main()
{
    printf("hello world\n");
    return 0;
}

字符串
“你好，ll”

@.str = private unnamed_addr constant [13 x i8] c"hello world\0A\00", align 1

; Function Attrs: noinline nounwind optnone
define dso_local i32 @main() #0 {
entry:
  %retval = alloca i32, align 4              // why does it have this pattern?
  store i32 0, i32* %retval, align 4
  %call = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str, i32 0, i32 0))
  ret i32 0
}

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

型
正常函数比较：
“hello_func. c”

#include <stdio.h>

int test()
{
    printf("hello world\n");
    return 0;
}

型
“hello_func.ll”

@.str = private unnamed_addr constant [13 x i8] c"hello world\0A\00", align 1

; Function Attrs: noinline nounwind optnone
define dso_local i32 @test() #0 {
entry:                               //  there is no pattern named retval
  %call = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([13 x i8], [13 x i8]* @.str, i32 0, i32 0))
  ret i32 0
}

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

型