On Thu, Oct 17, 2013 at 12:28:58PM +0300, Michael S. Tsirkin wrote: > On Thu, Oct 17, 2013 at 11:34:41AM +0300, Gleb Natapov wrote: > > On Thu, Oct 17, 2013 at 11:27:37AM +0300, Michael S. Tsirkin wrote: > > > On Thu, Oct 17, 2013 at 11:20:27AM +0300, Gleb Natapov wrote: > > > > On Thu, Oct 17, 2013 at 11:12:31AM +0300, Michael S. Tsirkin wrote: > > > > > On Thu, Oct 17, 2013 at 09:27:51AM +0300, Gleb Natapov wrote: > > > > > > On Wed, Oct 16, 2013 at 10:46:53PM +0300, Michael S. Tsirkin wrote: > > > > > > > Old GCC didn't let you reference variable by > > > > > > > number if it is listed with a specific register > > > > > > > constraint, on the assumption you can just > > > > > > > use the register name explicitly. > > > > > > > > > > > > > > Build fails with errors like this: > > > > > > > a.c:6: error: invalid 'asm': invalid operand code 'd' > > > > > > > > > > > > > Is it worth to support such ancient compiler? Nobody complained till > > > > > > now. > > > > > > > > > > Well it's not as widely used as kvm itself yet :) > > > > > The patch seems simple enough though. > > > > > > > > > > > BTW with your patch I still cannot compile with 4.2: > > > > > > > > > > > > x86/s3.c: In function 'main': > > > > > > x86/s3.c:145: error: inconsistent operand constraints in an 'asm' > > > > > > > > > > OK that's easy to fix. > > > > > > > > > > > > To fix, let's just use %eax %al etc. > > > > > > > > > > > > > Only %d0 does not work and dropping "d" fixes it since compiler can > > > > > > figure out correct register from variable size. The patch bellow fixes > > > > > > compilation for 4.2. > > > > > > > > > > It does produce warnings with -Wall though: > > > > > Assembler messages: > > > > > Warning: using `%ax' instead of `%eax' due to `w' suffix > > > > > Warning: using `%al' instead of `%eax' due to `b' suffix > > > > > > > > > Not for me. No warning with 4.7.3 and 4.2. .s file produced by gcc shows > > > > correct assembly with my patch. > > > > > > 4.3 doesn't. > > > > > I pretty much doubt that 4.2 and 4.7 produce correct assembly and 4.3 > > does not. Which file is it? Send me .s file produced by it. > > Tried to get it but problem went away after I reset and re-applied your > patch. I think I had some other change in there that > caused it, and blamed your patch incorrectly. Sorry. > NP, that makes more sense. > > > We have the "a" constraint there anyway - so what's the issue with just > > > writing %eax etc? I think it's safer than relying on compiler to do > > > the right thing. > > > > > It just papers over the problem. Compiler should either complain that it > > does not know what %w0 or complain that variable length does not match > > assembly > > Of course it can't. Compiler does not parse assembly at all: > these are just constant strings as far as it's concerned. > Compiler does not pars assembly itself but it parses things like %w0 to know what assembly to emit. That is why it complained about %d0 in the first place. > > or use correct register. > > Actually it does: it seems to correctly deduce > size from variable type. > > So your patch looks good to me, please apply. > > Will do. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
