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

[H.J. Lu via llvm-commits]

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.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20160304/ad95c10b/attachment.html>