[LLVMbugs] [Bug 594] NEW: [llvm-gcc] llvm-gcc lays out bitfields backwards on big endian systems

[bugzilla-daemon at cs.uiuc.edu]

http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=594

           Summary: [llvm-gcc] llvm-gcc lays out bitfields backwards on big
                    endian systems
           Product: tools
           Version: 1.0
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: normal
          Priority: P2
         Component: llvm-gcc
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: sabre at nondot.org


This program is miscompiled by LLVM on powerpc.  It appears that bitfields are
being layed out backwards by the CFE.  This may be related to Bug 449.  It
probably also affects Sparc.  This testcase should be compiled with
-fno-strict-aliasing.

-Chris


struct X {
   int A : 4;
   int Z : 28;
};

void test(struct X *P, int A) {
   P->A = A;
}

int main() {
  int Y = ~0;
  test((struct X*)&Y, 0);
  printf("%x\n", Y);
}



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