[llvm] r262727 - [ThinLTO] Ensure prevailing linkonce emitted as weak in ThinLTO backends

[Teresa Johnson via llvm-commits]

Done in r262745.

Thanks!

On Fri, Mar 4, 2016 at 1:16 PM, H.J. Lu <hjl.tools at gmail.com> wrote:

> Please check this in for me.
>
> Thanks.
>
> H.J.
>
> On Fri, Mar 4, 2016 at 1:15 PM, Teresa Johnson <tejohnson at google.com>
> wrote:
>
>> Thanks, H.J.
>>
>> Did you commit this or do you want me to go ahead and do that?
>>
>> Teresa
>>
>> On Fri, Mar 4, 2016 at 1:08 PM, H.J. Lu <hjl.tools at gmail.com> wrote:
>>
>>> On Fri, Mar 4, 2016 at 9:48 AM, Teresa Johnson via llvm-commits
>>> <llvm-commits at lists.llvm.org> wrote:
>>> > Author: tejohnson
>>> > Date: Fri Mar  4 11:48:35 2016
>>> > New Revision: 262727
>>> >
>>> > URL: http://llvm.org/viewvc/llvm-project?rev=262727&view=rev
>>> > Log:
>>> > [ThinLTO] Ensure prevailing linkonce emitted as weak in ThinLTO
>>> backends
>>> >
>>> > Summary:
>>> > Since IR files are all compiled into separate independent object files
>>> > in ThinLTO mode, the prevailing linkonce symbols must be emitted in its
>>> > object file even if it is no longer referenced there, e.g. if no
>>> > references remain in the module after inlining, since it may be
>>> > referenced by another ThinLTO compiled object file. This is done by
>>> > changing LDPR_PREVAILING_DEF_IRONLY* symbols to LDPR_PREVAILING_DEF,
>>> > which converts the prevailing linkonce to weak. We also don't need the
>>> > other prevailing IRONLY handling for internalization, which is not
>>> > currently performed for ThinLTO.
>>> >
>>> > Test case included.
>>> >
>>> > Reviewers: davidxl, rafael
>>> >
>>> > Subscribers: rafael, joker.eph, llvm-commits
>>> >
>>> > Differential Revision: http://reviews.llvm.org/D16173
>>> >
>>> > Added:
>>> >     llvm/trunk/test/tools/gold/X86/Inputs/thinlto_linkonceresolution.ll
>>> >     llvm/trunk/test/tools/gold/X86/thinlto_linkonceresolution.ll
>>> > Modified:
>>> >     llvm/trunk/tools/gold/gold-plugin.cpp
>>> >
>>> > Added:
>>> llvm/trunk/test/tools/gold/X86/Inputs/thinlto_linkonceresolution.ll
>>> > URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/tools/gold/X86/Inputs/thinlto_linkonceresolution.ll?rev=262727&view=auto
>>> >
>>> ==============================================================================
>>> > ---
>>> llvm/trunk/test/tools/gold/X86/Inputs/thinlto_linkonceresolution.ll (added)
>>> > +++
>>> llvm/trunk/test/tools/gold/X86/Inputs/thinlto_linkonceresolution.ll Fri
>>> Mar  4 11:48:35 2016
>>> > @@ -0,0 +1,4 @@
>>> > +target triple = "x86_64-unknown-linux-gnu"
>>> > +define linkonce_odr hidden void @f() {
>>> > +  ret void
>>> > +}
>>> >
>>> > Added: llvm/trunk/test/tools/gold/X86/thinlto_linkonceresolution.ll
>>> > URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/tools/gold/X86/thinlto_linkonceresolution.ll?rev=262727&view=auto
>>> >
>>> ==============================================================================
>>> > --- llvm/trunk/test/tools/gold/X86/thinlto_linkonceresolution.ll
>>> (added)
>>> > +++ llvm/trunk/test/tools/gold/X86/thinlto_linkonceresolution.ll Fri
>>> Mar  4 11:48:35 2016
>>> > @@ -0,0 +1,32 @@
>>> > +; RUN: llvm-as -function-summary %s -o %t.o
>>> > +; RUN: llvm-as -function-summary
>>> %p/Inputs/thinlto_linkonceresolution.ll -o %t2.o
>>> > +
>>> > +; Ensure the plugin ensures that for ThinLTO the prevailing copy of a
>>> > +; linkonce symbol is changed to weak to ensure it is not eliminated.
>>> > +; Note that gold picks the first copy of f() as the prevailing one,
>>> > +; so listing %t2.o first is sufficient to ensure that this copy is
>>> > +; preempted. Also, set the import-instr-limit to 0 to prevent f() from
>>> > +; being imported from %t2.o which hides the problem.
>>> > +; RUN: %gold -plugin %llvmshlibdir/LLVMgold.so \
>>> > +; RUN:     --plugin-opt=thinlto \
>>> > +; RUN:     --plugin-opt=-import-instr-limit=0 \
>>> > +; RUN:     --plugin-opt=save-temps \
>>> > +; RUN:     -o %t3.o %t2.o %t.o
>>> > +; RUN: llvm-nm %t3.o | FileCheck %s
>>> > +; RUN: llvm-dis %t.o.opt.bc -o - | FileCheck --check-prefix=OPT %s
>>> > +; RUN: llvm-dis %t2.o.opt.bc -o - | FileCheck --check-prefix=OPT2 %s
>>> > +
>>> > +; Ensure that f() is defined in resulting object file, and also
>>> > +; confirm the weak linkage directly in the saved opt bitcode files.
>>> > +; CHECK-NOT: U f
>>> > +; OPT: declare extern_weak hidden void @f()
>>> > +; OPT2: define weak_odr hidden void @f()
>>> > +
>>> > +target triple = "x86_64-unknown-linux-gnu"
>>>
>>> When you specify target triple, you should pass -m elf_x86_64
>>> to linker since the default linker target may be different.
>>>
>>>
>>> --
>>> H.J.
>>> ----
>>> diff --git a/test/tools/gold/X86/thinlto_linkonceresolution.ll
>>> b/test/tools/gold/X86/thinlto_linkonceresolution.ll
>>> index 044087b..e6ed95b 100644
>>> --- a/test/tools/gold/X86/thinlto_linkonceresolution.ll
>>> +++ b/test/tools/gold/X86/thinlto_linkonceresolution.ll
>>> @@ -7,7 +7,7 @@
>>>  ; so listing %t2.o first is sufficient to ensure that this copy is
>>>  ; preempted. Also, set the import-instr-limit to 0 to prevent f() from
>>>  ; being imported from %t2.o which hides the problem.
>>> -; RUN: %gold -plugin %llvmshlibdir/LLVMgold.so \
>>> +; RUN: %gold -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold.so \
>>>  ; RUN:     --plugin-opt=thinlto \
>>>  ; RUN:     --plugin-opt=-import-instr-limit=0 \
>>>  ; RUN:     --plugin-opt=save-temps \
>>>
>>
>>
>>
>> --
>> Teresa Johnson |  Software Engineer |  tejohnson at google.com |
>> 408-460-2413
>>
>
>
>
> --
> H.J.
>



-- 
Teresa Johnson |  Software Engineer |  tejohnson at google.com |  408-460-2413
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