[Bug tree-optimization/69196] code size regression with jump threading at -O2

sebastian.huber@embedded-brains.de gcc-bugzilla@gcc.gnu.org
Mon Jan 11 09:41:00 GMT 2016


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69196

--- Comment #4 from Sebastian Huber <sebastian.huber@embedded-brains.de> ---
I did a very rough check to see which code is faster on the PSIM/GDB simulator
using the following input data:

void printk(const char *fmt, ...)
{
  va_list ap;

  va_start(ap, fmt);
  vprintk(fmt, ap);
  va_end(ap);
}

void test(void)
{
  char *s = "x";
  printk("abc%sx%ix%cx%lu\n", s, 0, 'c', 1UL);
}

GCC 4.9: 311 time units

GCC 6: 316 time units

I guess its quite difficult to determine if this target independent code size
increase is actually a regression in general.  At least in this particular
function with this particular input data on this particular target/simulator
the code size is nearly doubled and the execution is slightly slower.


More information about the Gcc-bugs mailing list