[llvm-dev] Need help with code generation

[James Molloy via llvm-dev]

> A corrupted file could cause a fatal error or SEGV.

Uhhh, that's not particularly useful.

On Mon, 21 Mar 2016 at 19:02 Rui Ueyama <ruiu at google.com> wrote:

> On Sat, Mar 19, 2016 at 9:51 PM, 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?
>>
>
> You can use LLD as a library.
>
> https://github.com/llvm-mirror/lld/blob/master/docs/NewLLD.rst#the-elf-linker-as-a-library
>
>
>> 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
>>>>
>>>
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>>
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>>
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