Compiling this file:

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>

int main() {
  struct timeval now;
  return now.tv_usec % 15;
}

with this command,

g++ -c -fpeephole2 test.cpp


The problem goes away if "now.tv_usec" is casted to "int" a 32-bit number. So,
it's related to the fact it's a 64-bit integer.