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

[jakub at gcc dot gnu.org]

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

           Summary: x86_64 parameter passing unnecessary sign/zero extends
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: ja...@gcc.gnu.org
                CC: hubi...@gcc.gnu.org
            Target: x86_64-linux


It seems we zero/sign extend < 64-bit integral parameters into 64-bit registers
both on the caller and callee side on x86_64, one of those should be redundant.
In http://blog.regehr.org/archives/320 Example 4 it seems that LLVM probably
only zero/sign extends in the caller, not callee, not sure what ICC does.

__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);
}

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