* Simon McVittie: > - OK: any-i386, any-amd64
SSE2 is part of amd64 and i386, and has strict alignment requirements. This is why stack alignment bugs in the toolchain are usually fatal. (We still support SSE2-less i386 installations, I think, but some libraries will use SSE2 when available.) i386 also supports alignment checking. It used to be possible to run quite a bit of code with that flag switched on, but nowadays, glibc string functions use unaligned accesses in some cases because on current implementations, they are faster than the alternatives, so this way of debugging alignment issues no longer works. > - not OK: armel Many architectures take a significant performance hit. Usually, this is because unaligned accesses are emulated in a kernel trap (which can be switched off to debug these performance issues, hence the differences in system behavior). Some older i386/amd64 implementations have relatively costly unaligned access, too, but only in the order of a couple of cycles, not the hundreds or thousands kernel emulation will require. It is very difficult to write correct C code which uses unaligned pointers because they are an aliasing violtion as well. -- To UNSUBSCRIBE, email to debian-devel-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/87k32mfl41....@mid.deneb.enyo.de
