https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66852
--- Comment #7 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #6)
> So I suppose the IsAligned template is wrong.
Yes.
390 template <class T>
391 inline unsigned int GetAlignmentOf(T *dummy=NULL) // VC60 workaround
392 {
393 #ifdef CRYPTOPP_ALLOW_UNALIGNED_DATA_ACCESS
394 if (sizeof(T) < 16)
395 return 1;
396 #endif
397
398 #if (_MSC_VER >= 1300)
399 return __alignof(T);
400 #elif defined(__GNUC__)
401 return __alignof__(T);
402 #elif CRYPTOPP_BOOL_SLOW_WORD64
403 return UnsignedMin(4U, sizeof(T));
404 #else
405 return sizeof(T);
406 #endif
407 }
408
409 inline bool IsAlignedOn(const void *p, unsigned int alignment)
410 {
411 return alignment==1 || (IsPowerOf2(alignment) ?
ModPowerOf2((size_t)p, alignment) == 0 : (size_t)p % alignment == 0);
412 }
413
414 template <class T>
415 inline bool IsAligned(const void *p, T *dummy=NULL) // VC60 workaround
416 {
417 return IsAlignedOn(p, GetAlignmentOf<T>());
418 }
and
345 #if CRYPTOPP_BOOL_X64 || CRYPTOPP_BOOL_X86 || defined(__powerpc__)
346 #define CRYPTOPP_ALLOW_UNALIGNED_DATA_ACCESS
347 #endif
The only architecture where the assumption is valid is POWER8, where
unaligned vector loads are preferable to ones with forced-alignment.
