[Bug target/46942] x86_64 parameter passing unnecessary sign/zero extends

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46942

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> 2010-12-14 
17:13:19 UTC ---
__attribute__((noinline, noclone))
unsigned long f1 (unsigned int a, int b, unsigned short c, short d, unsigned
char e, signed char f)
{
  return (unsigned long) a + b + c + d + e + f;
}

unsigned long l;

unsigned long f2 (void)
{
  return f1 (l + 41, l + 41, l + 41, l + 41, l + 41, l + 41) + 1;
}

unsigned long f3 (unsigned int a, int b, unsigned short c, short d, unsigned
char e, signed char f)
{
  return f1 (a, b, c, d, e, f);
}

unsigned long f4 (int a, unsigned int b, short c, unsigned short d, signed char
e, unsigned char f)
{
  return f1 (a, b, c, d, e, f);
}

at -O2 shows in f4 that we can't trust that the sign/zero extension is done on
the caller side, at least we can't trust that it is sign/zero extended into
64-bits.