[Tinycc-devel] Buggy left shift on x86_64

[Vincent Lefevre]

I've found the following bug when compiling and testing MPFR with
Debian's tcc 0.9.26~git20120104.83d57c0-4 package.

On x86_64 (but not on i386), the left shift is buggy:

#include <stdio.h>
#include <limits.h>

#define SH (CHAR_BIT * sizeof(unsigned long) / 2)

int main (void)
{
  unsigned long m;
  int sh = SH;

  printf ("SH = %d\n", (int) SH);
  m = 1UL << SH;
  printf ("m = 0x%lx\n", m);
  m = 1UL << sh;
  printf ("m = 0x%lx\n", m);
  m = 1UL << (SH/2);
  m *= m;
  printf ("m = 0x%lx\n", m);

  return 0;
}

gives:

SH = 32
m = 0x0
m = 0x1
m = 0x100000000

The correct result (as obtained with gcc) is:

SH = 32
m = 0x100000000
m = 0x100000000
m = 0x100000000

I've also reported it on the Debian BTS:

  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=663711

-- 
Vincent Lefèvre <address@hidden> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)