On Tue, Apr 9, 2013 at 9:15 PM, Marc Glisse <marc.gli...@inria.fr> wrote: > On Tue, 9 Apr 2013, Marc Glisse wrote: > >> On Tue, 9 Apr 2013, Richard Biener wrote: >> >>> I seem to remember discussion in the PR(s) that the intrinsics should >>> (and do for other compilers) expand to the desired instructions even when >>> the corresponding instruction set is disabled. >> >> >> emmintrin.h starts with: >> #ifndef __SSE2__ >> # error "SSE2 instruction set not enabled" > > > Oh, re-reading your post, it looks like you mean we should change the > current behavior, not just avoid regressions... > > My opinion on the intrinsics is that they are the portable way to use > vectors on x86, but they are not equivalent to asm (which people should use > if they don't want the compiler looking at their code). Knowingly generating > SSE code with -mno-sse is not very appealing. > > However, the arguments in: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56298 > make sense. I guess I'll forget about this patch.
Note that to fully support emitting intrinsics "correctly" even without -msse x86 specific builtins need to be used and they need to conditionally expand to either UNSPECs (if the required instriuction set / modes are not available) or regular RTL (where they can be folded to generic GIMPLE earlier then as well). A complication is register allocation which would need to understand how to allocate registers for the UNSPECs - even if some of the modes would not be "available". So it's indeed a mess ... That said, folding of the x86 builtins to GIMPLE looks like a more viable approach that would not interfere too much with any possible route we would go here. As suggested previously please add a new target hook with the same interface as fold_stmt in case you want to work on this. Thanks, Richard. > -- > Marc Glisse
