[LLVMbugs] [Bug 16522] New: wrong code at optimization levels -Os and above (both 32-bit and 64-bit modes)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=16522

            Bug ID: 16522
           Summary: wrong code at optimization levels -Os and above (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 on
x86_64-linux-gnu at -Os and above (in both 32-bit and 64-bit modes). This is a
regression as both clang 3.2 and 3.3 produce correct code. 

$ clang-trunk -v
clang version 3.4 (trunk 185306)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang-trunk -Os reduced.c
$ a.out
-2
$ clang-3.3 -Os reduced.c
$ a.out
-1
$ clang-3.2 -Os reduced.c
$ a.out
-1
$ 


-------------------------------------------

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

int a, b = 1, *c = &a;

void 
foo (int p)
{
  int t; 
  for (t = 0; t < 16; t++)
    p ^= -1;
  *c = ~(p & b);
}

int
main ()
{
  foo (0);
  printf ("%d\n", a);
  return 0;
}

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