On 07/31/2017 09:40 AM, Florian Weimer wrote: > On 07/31/2017 05:15 PM, Jeff Law wrote: >> It's supposed to. My concern would be that most of the time a >> mis-aligned stack just works -- it's only when we see those key SSE2 >> instructions that it'll fault. So bugs in this support could stay >> latent for a long time. > > Exactly. I think GCC 6 was the first release were we saw GCC exploiting > struct alignment for SSE2 to heap objects (because the *other* tcmalloc, > in tchsh, did not follow ABI), and GCC 7 is the first release where we > saw SSE2 stack stores in the rather non-vectorizable malloc code in glibc. > > I'm pretty sure all hell would break lose if we shipped the i686 compat > userland with SSE2 optimization due to these issues, and I'm concerned > that all things considered, turning on SSE2 optimizations is probably > not worth the effort. Yea, you're probably right. Do you want to make the recommendation on behalf of GCC/GLBIC? jeff
