llvm/test/CFrontend/2007-04-11-InlineAsmUnion.c

// RUN: %llvmgcc %s -S -emit-llvm -o - | grep 'call void asm'

union U { int x; char* p; };
void foo() {
  union U bar;
  __asm__ volatile("foo %0\n" : "=r"(bar));
}