[Bug ipa/108695] [13 Regression] Wrong code since r13-5215-gb1f30bf42d8d47 for dd_rescue package

["marxin at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108695

--- Comment #6 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #5)
> I am 99% sure there is aliasing violations in this code too:
> #if _MSC_VER
> #define GETU32(p) SWAP(*((u32 *)(p)))
> #define PUTU32(ct, st)                                                  \
>         {                                                               \
>                 *((u32 *)(ct)) = SWAP((st));                            \
>         }

Yes, I'm also suspecting this code and I can verify that using optimize("O0")
for rijndaelEncrypt fixes the issue.

The thing below is cast from 'const u8 *' and I thought it's valid to case
to 'u32 *' and then access it. Can you explain to me how exactly the violation
happens?

> #else   /* _MSC_VER */
> # if __BYTE_ORDER == __BIG_ENDIAN
> #define GETU32(p) *((u32*)(p))
> #define PUTU32(ct, st) *((u32*)(ct)) = (st)
> #else   /* BIG_ENDIAN */
> #if 0 //def HAVE_LINUX_SWAB_H
> #define GETU32(p) __swab32(*((u32*)(p)))
> #define PUTU32(ct, st) *((u32*)(ct)) = __swab32((st))
> #else   /* __GNUC__ */
> #include <netinet/in.h>
> #define GETU32(p) ntohl(*((u32*)(p)))
> #define PUTU32(ct, st) *((u32*)(ct)) = htonl((st))
> #endif  /* __GNUC__ */
> #endif  /* BIG_ENDIAN */
> #endif  /*_MSC_VER */
> 

This part below is guarded with '#if 0'..

> #if 0
> #define GETU32(pt) (((u32)(pt)[0] << 24) ^ ((u32)(pt)[1] << 16) ^
> ((u32)(pt)[2] << 8) ^ ((u32)(pt)[3]))
> #define PUTU32(ct, st)                                                  \
>         {                                                               \
>                 (ct)[0] = (u8)((st) >> 24);                             \
>                 (ct)[1] = (u8)((st) >> 16);                             \
>                 (ct)[2] = (u8)((st) >> 8);                              \
>                 (ct)[3] = (u8)(st);                                     \
>         }
> #endif
> 
> A few other places too ...