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From: "sabre at nondot dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/37868] code that breaks TBAA is misoptimized even with -fno-strict-aliasing
Date: Sat, 18 Oct 2008 18:30:00 -0000	[thread overview]
Message-ID: <20081018182932.15689.qmail@sourceware.org> (raw)
In-Reply-To: <bug-37868-15165@http.gcc.gnu.org/bugzilla/>



------- Comment #1 from sabre at nondot dot org  2008-10-18 18:29 -------
Here is the testcase.  I should work with -fno-strict-aliasing:

#include <stdio.h>
#include <stdint.h>

struct X {
  unsigned char pad : 4;
  uint64_t a : 64;
  uint64_t b : 60;
} __attribute__((packed));

int main (void)
{
  struct X x;
  uint64_t bad_bits;

  x.pad = 255;
  x.a = -1ULL;
  x.b = -1ULL;

  bad_bits = ((uint64_t)-1ULL) ^ *(1+(uint64_t *) &x);
  printf("bad bits: %llx\n", bad_bits);
  return bad_bits != 0;
}


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37868


  reply	other threads:[~2008-10-18 18:30 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-18 18:17 [Bug tree-optimization/37868] New: code that doesn't " edwintorok at gmail dot com
2008-10-18 18:30 ` sabre at nondot dot org [this message]
2008-10-18 18:58 ` [Bug tree-optimization/37868] code that " rguenth at gcc dot gnu dot org
2008-10-18 22:36 ` rguenth at gcc dot gnu dot org
2008-10-18 22:44 ` rguenth at gcc dot gnu dot org
2008-10-22 11:48 ` [Bug tree-optimization/37868] [4.3 Regression] " rguenth at gcc dot gnu dot org
2008-10-22 13:50 ` rguenth at gcc dot gnu dot org
2008-11-03 11:29 ` jakub at gcc dot gnu dot org
2008-11-07 12:51 ` rguenth at gcc dot gnu dot org
2008-11-20 12:14 ` rguenth at gcc dot gnu dot org
2008-11-20 12:15 ` rguenth at gcc dot gnu dot org
2008-11-20 12:28 ` rguenth at gcc dot gnu dot org

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