Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx> 于2021年3月15日周一 下午11:00写道： > > On Fri, Mar 12, 2021 at 10:48:59AM +0000, YunQiang Su wrote: > > The MIPS FPU may have 3 mode: > > FR=0: MIPS I style, all of the FPR are single. > > FR=1: all 32 FPR can be double. > > FRE: redirecting the rw of odd-FPR to the upper 32bit of even-double FPR. > > > > The binary may have 3 mode: > > FP32: can only work with FR=0 and FRE mode > > FPXX: can work with all of FR=0/FR=1/FRE mode. > > FP64: can only work with FR=1 mode > > > > Some binary, for example the output of golang, may be mark as FPXX, > > while in fact they are FP32. It is caused by the bug of design and linker: > > Object produced by pure Go has no FP annotation while in fact they are FP32; > > if we link them with the C module which marked as FPXX, > > the result will be marked as FPXX. If these fake-FPXX binaries is executed > > in FR=1 mode, some problem will happen. > > > > In Golang, now we add the FP32 annotation, so the future golang programs > > won't have this problem. While for the existing binaries, we need a > > kernel workaround. > > what about just rebuilding them ? They are broken, so why should we fix > broken user binaries with kernel hacks ? > In fact without O32_FP64_SUPPORT option is enabled, the FP=0 mode is always used for FPXX. In fact it doesn't change the behaviour of kernel. > > Currently, FR=1 mode is used for all FPXX binary, it makes some wrong > > behivour of the binaries. Since FPXX binary can work with both FR=1 and FR=0, > > we force it to use FR=0 or FRE (for R6 CPU). > > I'm not sure, if I want to take this patch. > In fact, I'd prefer to use a config option to control this behivour. > Maciej, what's your take on this ? > > Thomas. > > -- > Crap can work. Given enough thrust pigs will fly, but it's not necessarily a > good idea. [ RFC1925, 2.3 ] -- YunQiang Su
