On Sun, 6 Sep 2015, Yousong Zhou wrote: > Hi, Maciej, first of all, thank you for your time on this, > appreciate it. You're welcome! > > The bug certainly was there, it's just your analysis and consequently the > > fix that are wrong in the general case for some reason, maybe a buggy > > compiler. > > > > This is the compiler "--version", > > mips-openwrt-linux-gcc (OpenWrt/Linaro GCC 4.8-2014.04 r46763) 4.8.3 A-ha! I've checked GCC's history and the symptom you're seeing was PR target/55777: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55777 and the bug has only been fixed pretty recently (r199328), already after GCC 4.8 has branched. From your troubles I infer the fix has not been backported to 4.8 and therefore is only available from GCC 4.9 up; of course either you or OpenWrt can still backport it and apply locally. Fortunately as I noted you need not dive into that hole as the reasonable choice here is to avoid the asm for MIPS16 code altogether, regardless of the GCC bug. > > Now if you stick `.set nomips16' just above WSBH, then this code will > > happily assemble, because this single instruction only (`.set pop' reverts > > any previous `.set' directives; I'm assuming you wrote above by hand and > > `.pop' is a typo) will assemble in the regular MIPS instruction mode. But > > if this code is ever reached, then the processor will still execute the > > machine code produced by the assembler from the WSBH instruction in the > > MIPS16 mode. > > Yes, I hand-copied it from the output of "gcc -S" just to > show the form/pattern (the original output is too long for > this conversation). No, that `.pop' is not a typo (I just > did a double-check). Well, please check again then as there's no such pseudo-op: $ cat pop.s .pop $ mips-mti-linux-gnu-as -o pop.o pop.s pop.s: Assembler messages: pop.s:1: Error: unknown pseudo-op: `.pop' $ > > No, it's your bug after all. I think the last paragraph I wrote quoted > > above combined with the source code in question make it clear what to do. > > Okay, I will try. Most of the time when textbooks read > clearly/obviously/apparently, things go astray ;) Well, if you really find yourself stuck with it, then come back for more hints, however please do try figuring it out yourself first as it'll be a good exercise. Maciej
