llvm-project/clang/test/CodeGen/designated-initializers.c

// RUN: %clang_cc1 -triple i386-unknown-unknown %s -emit-llvm -o - | FileCheck %s

struct foo {
    void *a;
    int b;
};

// CHECK: @u = global %union.anon zeroinitializer
union { int i; float f; } u = { };

// CHECK: @u2 = global %0 { i32 0, [4 x i8] undef }
union { int i; double f; } u2 = { };

// CHECK: @u3 = global %1 zeroinitializer
union { double f; int i; } u3 = { };

// CHECK: @b = global [2 x i32] [i32 0, i32 22]
int b[2] = {
  [1] = 22
};

int main(int argc, char **argv)
{
  // CHECK: internal global %struct.foo { i8* null, i32 1024 }
  static struct foo foo = {
    .b = 1024,
  };

  // CHECK: bitcast %union.anon* %u2
  // CHECK: call void @llvm.memset
   union { int i; float f; } u2 = { };

  // CHECK-NOT: call void @llvm.memset
  union { int i; float f; } u3;

  // CHECK: ret i32
}