Hi, Mark Thanks very much for your work, will apply your patches.
BTW, is there an easy way to test your patches? do you have such a test program? Best Regards, Wu Zhangjin On Sat, Oct 29, 2011 at 3:19 AM, Mark H Weaver <m...@netris.org> wrote: > Hello all, > > Apologies if this has already been addressed, as I am new to this > mailing list and have not had time to search the archives carefully. > > I have found and fixed the underlying cause of the illegal instruction > (SIGILL) signals sent to processes that execute some Loongson-specific > floating-point operations (e.g. an madd/msub/nmadd/nmsub instruction > with a quiet NaN or denormalized floating-point input value). > > MIPS and Loongson processors only implement the common cases of > floating-point arithmetic operations in hardware. In unusual cases, the > FPU signals an "Unimplemented instruction exception" and relies upon the > OS kernel to emulate the instruction in software. > > Linux includes a MIPS floating-point emulator to handle these cases, but > its emulator does not include support for the Loongson variants of > madd/msub/nmadd/nmsub. It also does not include support for the > Loongson operations on "paired-single" floating-point format (vectors of > two single-precision values). > > The following patches add support for these instructions to > arch/mips/math-emu. I fixed some other deficiencies in that code as > well, and those fixes are included in separate patches before the > Loongson2f patch. > > Note that during testing, I found a mistake in the documentation for the > Loongson 2F. Page 95 of Loongson2FUserGuide.pdf claims that the > paired-single floating-point instructions should use a format (fmt) > field of 11. However, the processor itself does not seem to recognize > instructions with (fmt=11). It seems to be looking for (fmt=22). > That's the case for the Loongson2F in my Yeeloong anyway (which > /proc/cpuinfo identifies as "ICT Loongson-2 V0.3 FPU V0.1"). > > I also found that the GNU assembler generates instructions with (fmt=22) > for most (but not all) of the paired-single floating-point instructions. > The only exceptions I've found are the Loongson-specific madd.ps, > msub.ps, nmadd.ps, and nmsub.ps instructions, for which GNU as generates > (fmt=11), although that does not work on my Loongson2F. Therefore, I > have also included a patch to GNU binutils (which will also apply to > GDB) to use fmt=22 for those instructions on Loongson2F. > > I should note that the documentation for Loongson 2E (not 2F) also > claims that the format field for paired-single instructions should use > fmt=11. I don't know whether this is a mistake or not, since I do not > have access to a Loongson 2E processor with which to test. > > Finally, two apologies are in order: > > * Ideally I should have added support for the entire set of MIPS 5 > floating-point operations, but I did not have time to do that job, nor > do I have a MIPS 5 processor with which to test. Therefore, these > patches address only the Loongson 2F. > > * I must admit that I have not tested these patches against the > linux-loongson-community kernel. However, I have tested them against > the linux--2.6.39.1-libre-lemote kernel maintained by Alexandre Oliva, > and there is no significant difference in arch/mips/math-emu between > those two trees. > > Comments and suggestions solicited. > > Mark > > > > -- > You received this message because you are subscribed to the Google Groups > "loongson-dev" group. > To post to this group, send email to loongson-dev@googlegroups.com. > To unsubscribe from this group, send email to > loongson-dev+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/loongson-dev?hl=en. > > > -- You received this message because you are subscribed to the Google Groups "loongson-dev" group. To post to this group, send email to loongson-dev@googlegroups.com. To unsubscribe from this group, send email to loongson-dev+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/loongson-dev?hl=en.
