[LLVMdev] Internalize pass

[Reid Kleckner]

Sounds like LLVM thinks the calling conventions or declarations are
mismatched.  See:
http://llvm.org/docs/FAQ.html#callconvwrong

Reid

On Sat, Oct 3, 2009 at 1:16 AM, Talin <viridia at gmail.com> wrote:
> Well, after some investigation I have a few more clues as to what is
> going on.
>
> I have a module which contains a call to an external native function.
> This native function lives in a static library, and there is an external
> declaration for it in the module.
>
> I find that I can run "llvm-ld -disable-opts -native -l mylibrary
> test.bc" and it works fine. That is, llvm-ld is able to generate a
> native object file, and link it against the static library with no problem.
>
> However, if I remove the "-disable-opts" line, it seems to replace the
> call to the native function with "unreachable". I'm not 100% certain of
> this, but if I replace the native function with a non-native function
> that does something similar, then it seems to work ok.
>
> Chris Lattner wrote:
>>
>> On Sep 30, 2009, at 12:06 AM, Talin wrote:
>>
>>> I'm playing around with different combinations of LTO passes, and
>>> I've run into a strange problem:
>>>
>>> I have a 'main' function that looks like this:
>>>
>>> define i32
>>> @"main(tart.core.Array[tart.core.String])->int"(%"tart.core.Array[tart.core.String]"*
>>> %args) {
>>> entry:
>>>   call void @llvm.dbg.func.start(metadata !0)
>>>   call void @llvm.dbg.stoppoint(i32 2, i32 19, metadata !1)
>>>   %integerLimitsTest = call { } @integerLimitsTest() ; <{ }> [#uses=0]
>>>   call void @llvm.dbg.stoppoint(i32 3, i32 21, metadata !1)
>>>   %integerToStringTest = call { } @integerToStringTest() ; <{ }>
>>> [#uses=0]
>>>   call void @llvm.dbg.stoppoint(i32 4, i32 9, metadata !1)
>>>   call void @llvm.dbg.region.end(metadata !0)
>>>   ret i32 0
>>> }
>>>
>>> However, when I add an internalize pass before the other LTO passes,
>>> the 'main' function turns into this:
>>>
>>> define i32 @main(i32, i8** nocapture) nounwind readnone {
>>> entry:
>>>   tail call void @llvm.dbg.func.start(metadata !0)
>>>   tail call void @llvm.dbg.stoppoint(i32 3, i32 21, metadata !1)
>>>   unreachable
>>> }
>>>
>>> The thing is, there's nothing particularly special or interesting
>>> about the functions being called from main().
>>
>> This is likely to not be due to internalize itself.  Internalize marks
>> functions "internal", which allows other interprocedural optimizers to
>> have more freedom to change their interfaces etc.  The likely problem
>> here is that you are calling something from 'main' with mismatching
>> calling conventions or something like that.  It is hard to say without
>> a full testcase.
>>
>> -Chris
>
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