llvm dev - Oct 2016 - ThinLTO: module-scope inline assembly blocks

On Mon, Oct 3, 2016 at 4:27 PM, Teresa Johnson <tejohnson at google.com>
wrote:
>
>
> On Mon, Oct 3, 2016 at 6:53 AM, Johan Engelen via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi all,
>>   I am trying to add ThinLTO to the LDC compiler. It seems to work well
>> on Mac (XCode 8) and Ubuntu (ld.gold + LLVMgold plugin).
>> However, I am running into trouble with module-scope inline assembly
>> blocks.
>>
>
> Are you adding the support using the new LTO API or using the libLTO C
> interfaces?
>
Perhaps I don't fully understand, but I think the answer is: neither :)
What I do is output the module as bitcode with the module summary index
added (`llvm::WriteBitcodeToFile`, summary index created with
`llvm::ModuleSummaryIndexBuilder`). This is then passed to the system
linker. The problems arise with ld.gold + LLVMgold plugin. I am using LLVM
3.9.0.
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Oh sorry, misunderstood and thought you were implementing in a new linker.
For gold you can pass -Wl,-plugin-opt,save-temps and look at the bitcode
after each phase of ThinLTO, e.g. I think the files will have .3.import.bc
extensions.

Teresa

On Mon, Oct 3, 2016 at 7:42 AM, Johan Engelen <jbc.engelen at gmail.com>
wrote:
> On Mon, Oct 3, 2016 at 4:27 PM, Teresa Johnson <tejohnson at
google.com>
> wrote:
>
>>
>>
>> On Mon, Oct 3, 2016 at 6:53 AM, Johan Engelen via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>>> Hi all,
>>>   I am trying to add ThinLTO to the LDC compiler. It seems to work
well
>>> on Mac (XCode 8) and Ubuntu (ld.gold + LLVMgold plugin).
>>> However, I am running into trouble with module-scope inline
assembly
>>> blocks.
>>>
>>
>> Are you adding the support using the new LTO API or using the libLTO C
>> interfaces?
>>
>
> Perhaps I don't fully understand, but I think the answer is: neither :)
> What I do is output the module as bitcode with the module summary index
> added (`llvm::WriteBitcodeToFile`, summary index created with
`llvm::ModuleSummaryIndexBuilder`).
> This is then passed to the system linker. The problems arise with ld.gold +
> LLVMgold plugin. I am using LLVM 3.9.0.
>
>

-- 
Teresa Johnson |  Software Engineer |  tejohnson at google.com |  408-460-2413
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With `save-temps` as plugin option, I get extra files for the MAIN module
(called `a.o`): `a.o.opt.bc` and `a.thinlto.bc`.
The `a.thinlto.bc` file contains nothing, only `source_filename = ...` .
The `a.o.opt.bc` (this looks like the result after ThinLTO importing and
optimization) contains the assembly block that it should not have:
```
module asm "\09.text"
module asm "\09.globl\09foo"
module asm "\09.align\0916, 0x90"
module asm "\09.type\09foo, at function"
module asm "foo:"
module asm "\09movq %rdi, %rax"
module asm "\09rorw $8, %ax"
module asm "\09ret "
module asm "\09.size\09foo, .-foo"
module asm ""
```
The asm is the same as in the other module (where it _should_ be defined),
and the linkage has not been changed.

Thanks for the help,
  Johan


On Mon, Oct 3, 2016 at 4:45 PM, Teresa Johnson <tejohnson at google.com>
wrote:
> Oh sorry, misunderstood and thought you were implementing in a new linker.
> For gold you can pass -Wl,-plugin-opt,save-temps and look at the bitcode
> after each phase of ThinLTO, e.g. I think the files will have .3.import.bc
> extensions.
>
> Teresa
>
> On Mon, Oct 3, 2016 at 7:42 AM, Johan Engelen <jbc.engelen at
gmail.com>
> wrote:
>
>> On Mon, Oct 3, 2016 at 4:27 PM, Teresa Johnson <tejohnson at
google.com>
>> wrote:
>>
>>>
>>>
>>> On Mon, Oct 3, 2016 at 6:53 AM, Johan Engelen via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>>
>>>> Hi all,
>>>>   I am trying to add ThinLTO to the LDC compiler. It seems to
work well
>>>> on Mac (XCode 8) and Ubuntu (ld.gold + LLVMgold plugin).
>>>> However, I am running into trouble with module-scope inline
assembly
>>>> blocks.
>>>>
>>>
>>> Are you adding the support using the new LTO API or using the
libLTO C
>>> interfaces?
>>>
>>
>> Perhaps I don't fully understand, but I think the answer is:
neither :)
>> What I do is output the module as bitcode with the module summary index
>> added (`llvm::WriteBitcodeToFile`, summary index created with
>> `llvm::ModuleSummaryIndexBuilder`). This is then passed to the system
>> linker. The problems arise with ld.gold + LLVMgold plugin. I am using
LLVM
>> 3.9.0.
>>
>>
>
>
> --
> Teresa Johnson |  Software Engineer |  tejohnson at google.com |
> 408-460-2413
>
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