[LLVMbugs] [Bug 16552] New: wrong code at -O3 on x86_64-linux-gnu (both 32-bit and 64-bit modes)

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Fri Jul 5 20:26:00 PDT 2013


            Bug ID: 16552
           Summary: wrong code at -O3 on x86_64-linux-gnu (both 32-bit and
                    64-bit modes)
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
          Assignee: unassignedclangbugs at nondot.org
          Reporter: su at cs.ucdavis.edu
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The following code is miscompiled by the current clang trunk and clang 3.3 on
x86_64-linux-gnu at -O3 in both 32-bit and 64-bit modes. This is a regression
from clang 3.2. 

Perhaps a different vectorizer bug as 16522? 

$ clang-trunk -v
clang version 3.4 (trunk 185684)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang-trunk -O3 reduced.c
$ a.out
$ clang-3.3 -O3 reduced.c
$ a.out
$ clang-3.2 -O3 reduced.c
$ a.out


int printf (const char *, ...);

int a = 1, b, d;
unsigned char c;

foo ()
  b |= 1;
  return a;

bar ()
l:d = foo () && --c;
  if (c)
    goto l;

main ()
  bar ();
  printf ("%d\n", b);
  return 0;

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