------- Comment #7 from rguenth at gcc dot gnu dot org 2010-02-09 23:18 ------- (In reply to comment #6) > > Your pointer isn't properly aligned to be accessed via uint32_t*. > > That's hardly satisfactory an answer. GCC has always generated working code > on > non-strict alignment platforms in this case and one can expect it to continue. > > Moreover, the psABI is explicit: > > "Like the Intel386 architecture, the AMD64 architecture in general does not > require all data accesses to be properly aligned. Misaligned data accesses are > slower than aligned accesses but otherwise behave identically. The only > exception is that __m128 must always be aligned properly." > > and there is no __m128 in the source code.
The C language standard says such pointer invokes undefined behavior. The non-working code is vectorized, and vectorized code can have strict alignment requirements. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43009
