Is this an optimizer bug?

From: Kasper Dupont (kasperd_at_daimi.au.dk)
Date: 05/31/05 

Date: Tue, 31 May 2005 09:19:59 +0200

If I compile this program with -O2, the write statement
is executed only once. If I compile it with -O1 the write
statement is executed multiple times as expected.

Looks like an optimizer bug to me. Did I miss something?

I'm running FC1 with kernel version 2.4.22-1.2199.nptl
and gcc version 3.3.2-1.

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>

#define PAGESIZE (1<<12)
#define PAGES (1<<18)

int main()
{
  int i;
  char *mem;
  mem=mmap(NULL,PAGESIZE*PAGES,PROT_READ|PROT_WRITE,
           MAP_PRIVATE|MAP_ANONYMOUS,0,0);
  if (mem==MAP_FAILED) {
    perror("mmap");
    return EXIT_FAILURE;
  }

  for (i=0;i<PAGES;++i)
    if (write(1,mem+i*PAGESIZE,PAGESIZE)<1) {
      perror("write");
      return EXIT_FAILURE;
    }

  return 0;
} 

-- 
Kasper Dupont -- der bruger for meget tid på usenet.
Note to self: Don't try to allocate 256000 pages
with GFP_KERNEL on x86.

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