On 07/11/15 09:23, Segher Boessenkool wrote: > On Fri, Nov 06, 2015 at 11:50:40PM -0800, David Wohlferd wrote: >>> The same goes for some constraints and almost all output modifiers. >> >> Are you suggesting more doc changes? Looking thru the pages you reference: >> >> - Starting with 'modifiers', "=+&" and (reluctantly) "%" seem reasonable >> for inline asm. But both "#*" seem sketchy. > > Output modifiers, not constraint modifiers -- things like "%X0" in > the output template. Many are only useful in the machine description, > but some (like that 'X' for rs6000) are vital for asm as well. >
They're not just useful, they're essential on AArch64 and ARM. They're needed, for example, to get the 32/64-bit register sizing correct. R. >> - Under 'simple constraints', "mringX" all (more or less) make sense to >> me. But "oV<>sp" are not things I can envision using. > > Some are more useful on some targets than on others, sure. But these > generic constraints are extremely unlikely to ever get a change; this > is not true for target constraints. If we want to delete (or change > semantics of) some target constraint, and that constraint is documented, > we have to fear the ire of the one or two users of that constraint. > >> - The 'machine constraints' for i386 (the only machine I know) all seem >> reasonable. However for platforms that support autoincrement >> (powerpc?), apparently using "m" needs more docs (per >> https://gcc.gnu.org/ml/gcc/2008-03/msg01079.html). > > I think the manual (the "Simple Constraints" section) does describe it > all, but it could be clearer. The PowerPC 'm' description does a good > job of explaining things further (for that target). > >> Are these the things to which you are referring? I've always assumed >> the parts that seem obscure here were due to my i386-centric view of the >> world. Are some of them actually md-only? > > Almost everything can be used in asm as well, but many constraints etc. > are much less useful there. > >> There are other minor changes I'd make on some of these pages. But >> mostly they are not worth it unless I'm doing something else there too. >> So if there's something here you think needs changing, let me know and >> I'll take a crack at it. >> >> Other than that, I'll keep working my way thru the doc issues in the >> inline-asm bugs. I've done what I can for 10396. > > Thanks again :-) > > > Segher >
