[LLVMbugs] [Bug 22376] New: Negative zero misoptimized

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22376

            Bug ID: 22376
           Summary: Negative zero misoptimized
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: sunil_srivastava at playstation.sony.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

The following example fails with –O2 (passes at -O1)

extern "C"  int printf(const char *, ...);
int signbit(double d) {return *((long long *)&d)<0;}
double m0 = -0.;
int main() {
  if ( m0 == 0) {
    if  (signbit(m0) != 0)
      printf("Passed\n");
    else
      printf("Failed\n");
  }
}

It is a regression since r225660, which was for Bug 17713.

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