llvm-project/clang/test/CodeGen/2007-05-29-UnionCopy.c

// RUN: %clang_cc1 -emit-llvm -o - %s | grep memcpy
// PR1421

struct A {
  char c;
  int i;
};

struct B {
  int c;
  unsigned char x;
};

union U { struct A a; struct B b; };

void check(union U *u, union U *v) {
  *u = *v;
}