[LLVMbugs] [Bug 12612] New: Assertion raised: Pointer is not sufficiently aligned in PointerIntPair::setPointer

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12612

             Bug #: 12612
           Summary: Assertion raised:  Pointer is not sufficiently aligned
                    in PointerIntPair::setPointer
           Product: libraries
           Version: trunk
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Support Libraries
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: wuye9036 at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Hi guys,
  When I am compiling a code as following
  void set(i32* ret, i32 v)
    store i32 v, i32* ret

 Following assertion was raised:

  Assertion failed: (PtrVal % (1 << PtrTraits::NumLowBitsAvailable) == 0) &&
"Poin
ter is not sufficiently aligned", file
D:\Programming\salvia\3rd_party\llvm\incl
ude\llvm/ADT/PointerIntPair.h, line 79

 I've trace into code,

  void setPointer(PointerTy Ptr) {
    intptr_t PtrVal
      = reinterpret_cast<intptr_t>(PtrTraits::getAsVoidPointer(Ptr));
    assert( (PtrVal & (1 << PtrTraits::NumLowBitsAvailable)-1) == 0) &&
"Pointer is not sufficiently aligned");
    // Preserve all low bits, just update the pointer.
    Value = PtrVal | (Value & ~PointerBitMask);
  }      

 And now PointerTy is IndexListEntry, and PtrVal is address of object.

 In PtrTraits, NumLowBitAvailable is 3 when type is IndexListEntry. So
assertion need PtrVal is 8-byte aligned.

 But when entry is creating, the alignOf<IndexListEntry>() is 4. 

 IndexListEntry *entry =
   static_cast<IndexListEntry*>(
   ileAllocator.Allocate(sizeof(IndexListEntry),
   alignOf<IndexListEntry>()));

 I think that's the reason why this assertion is raised.

 Thank you.

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