[Bug tree-optimization/80588] New: GCC can't simplify static inline function with xor/xnor

[SztfG at yandex dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80588

            Bug ID: 80588
           Summary: GCC can't simplify static inline function with
                    xor/xnor
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: SztfG at yandex dot ru
  Target Milestone: ---

GCC can't simplify static inline function for xor/xnor, but can, if used macro
instead. Testcase:

#include <inttypes.h>

#define TYPE uint8_t

#define M_XOR(a,b) ((!!(a))^(!!(b)))
#define M_NXOR(a,b) (!((!!(a))^(!!(b))))

__attribute__((__always_inline__, const))
static inline TYPE m_xor (const TYPE a, const TYPE b)
{
    return M_XOR(a,b);
}

__attribute__((__always_inline__, const))
static inline TYPE m_xnor (const TYPE a, const TYPE b)
{
    return M_NXOR(a,b);
}

// bad assembly output
int test1b(const TYPE a, const TYPE b)
{
    return m_xor(a,b) == !m_xnor(a,b);
}

int test2b(const TYPE a, const TYPE b)
{
    return !m_xor(a,b) == m_xnor(a,b);
}

int test3b(const TYPE a, const TYPE b)
{
    return M_XOR(a,b) == !m_xnor(a,b);
}

// good assembly output
int test1g(const TYPE a, const TYPE b)
{
    return m_xor(a,b) == M_XOR(a,b);
}

int test2g(const TYPE a, const TYPE b)
{
    return M_XOR(a,b) == !M_NXOR(a,b);
}

int test3g(const TYPE a, const TYPE b)
{
    return M_XOR(a,b) != !M_NXOR(a,b);;
}