// Using Clang/LLVM 3.6.0 we are observing a case where the optimizations
// are clobbering EFLAGS on x86_64.  This is inconvenient when the status of
// bit 9 (IF), which controls interrupts, changes.
//
// Here's a simple test program.  Assume that the external function foo()
// modifies the IF bit in EFLAGS.
//
// And it's compiled using the following command line:
//
// $ clang -O2 -c -o clang-eflag.o clang-eflag.c
//
// Check objdump output using the following command line:
//
// $ objdump -S clang-eflag.o
//
// For more details see "[LLVMdev] optimizer clobber EFLAGS"
// <http://lists.llvm.org/pipermail/llvm-dev/2015-July/088766.html>

#include <stdlib.h>
#include <stdbool.h>

void foo(void);
int a;

int bar(void)
{
        foo();

        bool const zero = a -= 1;

        asm volatile ("" : : : "cc");
        foo();

        if (zero) {
                return EXIT_FAILURE;
        }

        foo();

        return EXIT_SUCCESS;
}