Hi Claudiu, Thanks a lot for the clarifications! Unfortunately, though I have looked at what you suggested, I still can't quite understand how to emit and work with RTL that will ultimately lower into the assembly required for TLS on Windows in legitimize_tls_address :( I shall not test your patience and bother you any more by bombarding you with repeated questions over and over, but once again, thanks for the help!
CC-ing Jan Hubicka, who is an i386 maintainer, which is the platform that I aim to implement TLS for an OS for (x86 and x64 Windows) and who's area of expertise may help here best regards, Julian On Wed, Jul 24, 2024 at 4:18 PM Claudiu Zissulescu Ianculescu < claz...@gmail.com> wrote: > Hi Julian, > > I hope you have Ulrich's document about TLS, if not please google it: > "ELF Handling for Thread-Local Storage - Ulrich Drepper" > > In ARC, I used unspec constructions to emit TLS addresses. If you > wanna simplify it, in the legitimzie_tls_address you can only > implement the most general case, namely TLS_GLOBAL_DYNAMIC, and all > the others to fall back to it. For TLS, you need to reserve a tls > register which will hold the tls pointer (in arc is a register holded > by arc_tp_regno variable, but in ur case u can fix it). > U can use the tls examples in the gcc's dejagnu test folder, compile > arc backend and check the output assembly to see how it works. > In case of ARC, the global dynamic model generates two relocs: > > add r0,pcl,@x@tlsgd # R_ARC_TLS_GD_GOT x > bl @__tls_get_addr@plt # R_ARC_S21_PCREL_PLT __tls_get_addr > # Address of x in r0 > > where __tls_get_addr is a function provided by the OS which will > return the address of variable x in r0 (return reg). You should > already have the PLT reloc, and you need to implement the TLS_GD_GOT > reloc to GOT table. In GOT table you need additionally two relocs: > GOT[n] R_ARC_TLS_DTPMOD x > GOT[n+1] R_ARC_TLS_DTPOFF x > > I hope this may clarify it a bit, cheers, > Claudiu > > On Thu, Jul 18, 2024 at 12:43 PM Julian Waters via Gcc <gcc@gcc.gnu.org> > wrote: > > > > I guess I'll just say what platform I want to implement this for, since > the > > roundabout way of talking about it is probably confusing to everyone. > It's > > Windows, and hopefully implementing TLS for it should be relatively > easier > > since there is only 1 TLS model on Windows > > > > best regards, > > Julian > > > > On Thu, Jul 18, 2024 at 5:39 PM Julian Waters <tanksherma...@gmail.com> > > wrote: > > > > > Hi Claudiu, > > > > > > Thanks for the tip, I've since looked at and drawn inspiration from > > > arc.cc. The main issue I have now is how to implement the code in > > > legitimize_tls_address under i386.cc and the corresponding i386.md > machine > > > description file to get the following assembly for a TLS read (Assuming > > > that local is the name of the thread local variable, that the last mov > > > depends on the size of the variable, since it would be movq if it was > an 8 > > > byte variable, that rscratch refers to scratch registers, and that > > > rscratch1 holds the read TLS value at the end of the operation): > > > > > > movl _tls_index(%rip), %rscratch1 > > > movq %gs:88, %rscratch2 > > > movq (%rscratch2, %rscratch1, 8), %rscratch1 > > > movl local@SECREL32(%rscratch1), %rscratch1 > > > > > > With some reference from the arc.cc code and another (unofficial) patch > > > for the platform that I want to implement TLS for, I've managed a half > > > finished implementation of TLS, but the final blocker so to speak is my > > > lack of understanding on how the RTL manipulating code in > > > legitimize_tls_address works. If you have any pointers on how to > manipulate > > > RTL to get the assembly required as seen above, I would be very much > > > grateful :) > > > > > > best regards, > > > Julian > > > > > > On Tue, Jul 16, 2024 at 8:16 PM Claudiu Zissulescu Ianculescu < > > > claz...@gmail.com> wrote: > > > > > >> Hi Julian, > > >> > > >> You can check how we did it for ARC. In a nutshell, you need to define > > >> HAVS_AS_TLS macro, you need to legitimize the new TLS address and > > >> calls. Please have a look in arc.cc and search for TLS, also use git > > >> blame to see the original patches. Of course, there are different ways > > >> to implement TLS, in ARC is the simplest solution. Also, u need to > > >> hack the assembler, linker and the OS for a full implementation. > > >> > > >> Cheers, > > >> Claudiu > > >> > > >> On Tue, Jul 9, 2024 at 7:14 PM Julian Waters via Gcc <gcc@gcc.gnu.org > > > > >> wrote: > > >> > > > >> > Hi all, > > >> > > > >> > I'm currently trying to implement Native TLS on a platform that gcc > uses > > >> > emutls for at the moment, but I can't seem to figure out where and > how > > >> to > > >> > implement it. I have a rough idea of the assembly required for TLS > on > > >> this > > >> > platform, but I don't know where to plug it in to the compiler to > make > > >> it > > >> > work. Could someone point me in the right direction for > implementing TLS > > >> > for a platform that doesn't have it implemented at the moment? > > >> > > > >> > I'm aware that I am being vague as to which platform I want to > > >> implement it > > >> > for. It's a platform that is likely low priority in the eyes of > most gcc > > >> > maintainers, so I'm deliberately avoiding mentioning what platform > it > > >> is so > > >> > I don't get crickets for a reply :) > > >> > > > >> > best regards, > > >> > Julian > > >> > > > >
