mats petersson via llvm-dev
2016-Mar-19 20:58 UTC
[llvm-dev] Need help with code generation
If you plan on calling C runtime library functions, you probably want to do what I did: Cheat, and make a libruntime.a (with C functions to do stuff your compiler can't do natively) and then link that using clang or gcc. https://github.com/Leporacanthicus/lacsap/blob/master/binary.cpp#L124 At some point, I plan to replace my runtime library with native Pascal code, at which point I will be able to generate the ELF binary straight from my compiler without the runtime library linking in the C runtime library, but that's not happening anytime real soon. Getting the compiler to compile v5 of Wirth's original Pascal compiler is higher on the list... :) -- Mats On 19 March 2016 at 20:51, James Molloy via llvm-dev < llvm-dev at lists.llvm.org> wrote:> Hi Lorenzo, > > Clang doesn't call llc; LLVM is compiled into Clang. Clang does call the > system linker though. > > Making your compiler generate *object* code is very simple. Making it > fixup that object code and execute it in memory (JIT style) is also simple. > Linking it properly and creating a fixed up ELF file is less simple. For > that, you need to compile to object (using addPassesToEmitFile() - see > llc.cpp) then invoke a linker. Getting that command line right can be quite > difficult. > > Rafael, This would be a good usecase for LLD as a library. I heard that > this is is an explicit non-goal, which really surprised me. Is that indeed > the case? > > Cheers, > > James > > On Sat, 19 Mar 2016 at 13:32 Lorenzo Laneve via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> I'd like to make my compiler independent, just like Clang. Doesn't Clang >> call llc and then system's ld by itself? I don't want my compiler to depend >> by any other program. >> I guess there will be a class in the llvm library that generates the >> object files based on the system's triple and data layout, and then call >> the system's ld? >> >> On Mar 19, 2016, at 11:48 AM, Bruce Hoult <bruce at hoult.org> wrote: >> >> If you've created a .bc or a .ll file then the simplest thing is to just >> give it to clang exactly the same as you would for a .c file. Clang will >> just Do The Right Thing with it. >> >> If you don't want to link, then pass flags such as -c to clang as usual. >> >> e.g. >> >> ---- hello.ll ---- >> declare i32 @puts(i8*) >> @str = constant [12 x i8] c"Hello World\00" >> >> define i32 @main() { >> %1 = call i32 @puts(i8* getelementptr inbounds ([12 x i8]* @str, i64 0, >> i64 0)) >> ret i32 0 >> } >> ---------------- >> >> $ clang hello.ll -o hello && ./hello >> warning: overriding the module target triple with >> x86_64-apple-macosx10.10.0 >> 1 warning generated. >> Hello World >> >> >> On Sat, Mar 19, 2016 at 3:03 AM, Lorenzo Laneve via llvm-dev < >> llvm-dev at lists.llvm.org> wrote: >> >>> I wrote my compiler and now it generates LLVM IR modules. Now i’d like >>> to go ahead and make object file and then executable, just like clang does. >>> >>> What should I have to use to create the object files? and then how do I >>> call the ld? (not llvm-ld, I want my compiler to work like Clang and I read >>> that Clang doesn’t use llvm-ld). >>> _______________________________________________ >>> LLVM Developers mailing list >>> llvm-dev at lists.llvm.org >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >>> >> >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160319/ba83690a/attachment.html>
Lorenzo Laneve via llvm-dev
2016-Mar-19 22:15 UTC
[llvm-dev] Need help with code generation
@james Yeah for code generation I figured out that clang doesn't actually use llc, and I already started reading its code to see how it works. For the ld, there's not an "helper" in the llvm library that calls it, is there? By the way, I thought about calling ld with things like execl() or std::system(), I don't know if it's a good idea, I'm always afraid there are better ways than mine! @mats Yea, I haven't used C's system calls in my own code yet but if I just have to declare the function puts in the IR modules (e.g.: putc) and then link against libc, am I right? Should I use basic C functions such as putc() and getc(), in my runtime library or is there a more efficient way to set up my runtime library?> On Mar 19, 2016, at 9:58 PM, mats petersson <mats at planetcatfish.com> wrote: > > If you plan on calling C runtime library functions, you probably want to do what I did: > Cheat, and make a libruntime.a (with C functions to do stuff your compiler can't do natively) and then link that using clang or gcc. > > https://github.com/Leporacanthicus/lacsap/blob/master/binary.cpp#L124 > > At some point, I plan to replace my runtime library with native Pascal code, at which point I will be able to generate the ELF binary straight from my compiler without the runtime library linking in the C runtime library, but that's not happening anytime real soon. Getting the compiler to compile v5 of Wirth's original Pascal compiler is higher on the list... :) > > -- > Mats > >> On 19 March 2016 at 20:51, James Molloy via llvm-dev <llvm-dev at lists.llvm.org> wrote: >> Hi Lorenzo, >> >> Clang doesn't call llc; LLVM is compiled into Clang. Clang does call the system linker though. >> >> Making your compiler generate *object* code is very simple. Making it fixup that object code and execute it in memory (JIT style) is also simple. Linking it properly and creating a fixed up ELF file is less simple. For that, you need to compile to object (using addPassesToEmitFile() - see llc.cpp) then invoke a linker. Getting that command line right can be quite difficult. >> >> Rafael, This would be a good usecase for LLD as a library. I heard that this is is an explicit non-goal, which really surprised me. Is that indeed the case? >> >> Cheers, >> >> James >> >>> On Sat, 19 Mar 2016 at 13:32 Lorenzo Laneve via llvm-dev <llvm-dev at lists.llvm.org> wrote: >>> I'd like to make my compiler independent, just like Clang. Doesn't Clang call llc and then system's ld by itself? I don't want my compiler to depend by any other program. >>> I guess there will be a class in the llvm library that generates the object files based on the system's triple and data layout, and then call the system's ld? >>> >>>> On Mar 19, 2016, at 11:48 AM, Bruce Hoult <bruce at hoult.org> wrote: >>>> >>>> If you've created a .bc or a .ll file then the simplest thing is to just give it to clang exactly the same as you would for a .c file. Clang will just Do The Right Thing with it. >>>> >>>> If you don't want to link, then pass flags such as -c to clang as usual. >>>> >>>> e.g. >>>> >>>> ---- hello.ll ---- >>>> declare i32 @puts(i8*) >>>> @str = constant [12 x i8] c"Hello World\00" >>>> >>>> define i32 @main() { >>>> %1 = call i32 @puts(i8* getelementptr inbounds ([12 x i8]* @str, i64 0, i64 0)) >>>> ret i32 0 >>>> } >>>> ---------------- >>>> >>>> $ clang hello.ll -o hello && ./hello >>>> warning: overriding the module target triple with x86_64-apple-macosx10.10.0 >>>> 1 warning generated. >>>> Hello World >>>> >>>> >>>>> On Sat, Mar 19, 2016 at 3:03 AM, Lorenzo Laneve via llvm-dev <llvm-dev at lists.llvm.org> wrote: >>>>> I wrote my compiler and now it generates LLVM IR modules. Now i’d like to go ahead and make object file and then executable, just like clang does. >>>>> >>>>> What should I have to use to create the object files? and then how do I call the ld? (not llvm-ld, I want my compiler to work like Clang and I read that Clang doesn’t use llvm-ld). >>>>> _______________________________________________ >>>>> LLVM Developers mailing list >>>>> llvm-dev at lists.llvm.org >>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >>> _______________________________________________ >>> LLVM Developers mailing list >>> llvm-dev at lists.llvm.org >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160319/e506a4a4/attachment.html>
Yes, you shouldn't have any trouble just declaring and using C functions such as fopen, fclose, puts, fputs, fputc. You're likely to find that putc is a macro not a function, in which case you won't be able to use that. Depending on whether it's important, if you're running on a Unix-like system then you could save quite a bit of size in your binary by using open(2), close(2), read(2), write(2) directly, as they're not any harder to use. But the C standard library is available in more places. On Sun, Mar 20, 2016 at 1:15 AM, Lorenzo Laneve via llvm-dev < llvm-dev at lists.llvm.org> wrote:> @james > Yeah for code generation I figured out that clang doesn't actually use > llc, and I already started reading its code to see how it works. > For the ld, there's not an "helper" in the llvm library that calls it, is > there? > By the way, I thought about calling ld with things like execl() or > std::system(), I don't know if it's a good idea, I'm always afraid there > are better ways than mine! > > > @mats > Yea, I haven't used C's system calls in my own code yet but if I just have > to declare the function puts in the IR modules (e.g.: putc) and then link > against libc, am I right? > Should I use basic C functions such as putc() and getc(), in my runtime > library or is there a more efficient way to set up my runtime library? > > On Mar 19, 2016, at 9:58 PM, mats petersson <mats at planetcatfish.com> > wrote: > > If you plan on calling C runtime library functions, you probably want to > do what I did: > Cheat, and make a libruntime.a (with C functions to do stuff your compiler > can't do natively) and then link that using clang or gcc. > > https://github.com/Leporacanthicus/lacsap/blob/master/binary.cpp#L124 > > At some point, I plan to replace my runtime library with native Pascal > code, at which point I will be able to generate the ELF binary straight > from my compiler without the runtime library linking in the C runtime > library, but that's not happening anytime real soon. Getting the compiler > to compile v5 of Wirth's original Pascal compiler is higher on the list... > :) > > -- > Mats > > On 19 March 2016 at 20:51, James Molloy via llvm-dev < > llvm-dev at lists.llvm.org> wrote: > >> Hi Lorenzo, >> >> Clang doesn't call llc; LLVM is compiled into Clang. Clang does call the >> system linker though. >> >> Making your compiler generate *object* code is very simple. Making it >> fixup that object code and execute it in memory (JIT style) is also simple. >> Linking it properly and creating a fixed up ELF file is less simple. For >> that, you need to compile to object (using addPassesToEmitFile() - see >> llc.cpp) then invoke a linker. Getting that command line right can be quite >> difficult. >> >> Rafael, This would be a good usecase for LLD as a library. I heard that >> this is is an explicit non-goal, which really surprised me. Is that indeed >> the case? >> >> Cheers, >> >> James >> >> On Sat, 19 Mar 2016 at 13:32 Lorenzo Laneve via llvm-dev < >> llvm-dev at lists.llvm.org> wrote: >> >>> I'd like to make my compiler independent, just like Clang. Doesn't Clang >>> call llc and then system's ld by itself? I don't want my compiler to depend >>> by any other program. >>> I guess there will be a class in the llvm library that generates the >>> object files based on the system's triple and data layout, and then call >>> the system's ld? >>> >>> On Mar 19, 2016, at 11:48 AM, Bruce Hoult <bruce at hoult.org> wrote: >>> >>> If you've created a .bc or a .ll file then the simplest thing is to just >>> give it to clang exactly the same as you would for a .c file. Clang will >>> just Do The Right Thing with it. >>> >>> If you don't want to link, then pass flags such as -c to clang as usual. >>> >>> e.g. >>> >>> ---- hello.ll ---- >>> declare i32 @puts(i8*) >>> @str = constant [12 x i8] c"Hello World\00" >>> >>> define i32 @main() { >>> %1 = call i32 @puts(i8* getelementptr inbounds ([12 x i8]* @str, i64 >>> 0, i64 0)) >>> ret i32 0 >>> } >>> ---------------- >>> >>> $ clang hello.ll -o hello && ./hello >>> warning: overriding the module target triple with >>> x86_64-apple-macosx10.10.0 >>> 1 warning generated. >>> Hello World >>> >>> >>> On Sat, Mar 19, 2016 at 3:03 AM, Lorenzo Laneve via llvm-dev < >>> llvm-dev at lists.llvm.org> wrote: >>> >>>> I wrote my compiler and now it generates LLVM IR modules. Now i’d like >>>> to go ahead and make object file and then executable, just like clang does. >>>> >>>> What should I have to use to create the object files? and then how do I >>>> call the ld? (not llvm-ld, I want my compiler to work like Clang and I read >>>> that Clang doesn’t use llvm-ld). >>>> _______________________________________________ >>>> LLVM Developers mailing list >>>> llvm-dev at lists.llvm.org >>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >>>> >>> >>> _______________________________________________ >>> LLVM Developers mailing list >>> llvm-dev at lists.llvm.org >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >>> >> >> _______________________________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> >> > > _______________________________________________ > LLVM Developers mailing list > llvm-dev at lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev > >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20160320/9bbc3116/attachment-0001.html>