[llvm] r274699 - ThinLTO: Add test cases for promote+internalize.

Tue Jul 25 20:03:14 PDT 2017

I'm not sure either of us are making much sense of what this test does, or
is intended to do - I think it's best to just remove it.

On Tue, Jul 25, 2017 at 7:51 PM Peter Collingbourne <peter at pcc.me.uk> wrote:

> On Tue, Jul 25, 2017 at 5:52 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>>
>>
>> On Tue, Jul 25, 2017 at 5:49 PM David Blaikie <dblaikie at gmail.com> wrote:
>>
>>> On Tue, Jul 25, 2017 at 4:24 PM Peter Collingbourne <peter at pcc.me.uk>
>>> wrote:
>>>
>>>> On Tue, Jul 25, 2017 at 2:29 PM, David Blaikie <dblaikie at gmail.com>
>>>> wrote:
>>>>
>>>>> Hey Peter,
>>>>>
>>>>> Bit of thread necromancy here - but I'm trying to change some things
>>>>> wrt alias+linkonce_odr (going to make it behave like the alias+external
>>>>> case, for simplicity, less duplication, and simplified debug info) & this
>>>>> test is failing:
>>>>>
>>>>> My change causes none of the aliasees to be imported (not even those
>>>>> linkonce_odr ones).
>>>>>
>>>>
>>>> Is that a good idea? I would have thought that we'd want to go in the
>>>> opposite direction and try to import more functions that use aliases. I
>>>> believe that is blocked on support for available_externally aliases though
>>>> (this thread has the most recent discussion I can find on that topic:
>>>> http://lists.llvm.org/pipermail/llvm-dev/2017-January/109227.html).
>>>>
>>>
>>> Right, ultimately that's the right direction - this functionality
>>> though, is a dead-end, it's not a stepping stone towards that outcome - and
>>> it gets in the way (specifically it gets in the way of debug info, but also
>>> means thinlto backend objects are larger than they need to be - by having
>>> linkonce functions when they could be relying on the
>>> linkonce-promoted-to-weak definition) without any specific reason to
>>> believe the benefit (optimizing across aliases of linkonce_odr functions)
>>> is significant.
>>>
>>>
>>>>
>>>> This causes -thinlto-action=internalize to fail ("-internalize will not
>>>>> perform without -exportedsymbol").
>>>>>
>>>>
>>>> Is it really failing because of that?
>>>> http://llvm-cs.pcc.me.uk/tools/llvm-lto/llvm-lto.cpp#618
>>>> Looks like it just prints a warning.
>>>>
>>>
>>> Yep, it prints a warning & then doesn't internalize anything/is a no-op,
>>> as per the warning.
>>>
>>
> That warning is misleading because the condition it tests for is not the
> same as the one that ThinLTOCodeGenerator uses.
> http://llvm-cs.pcc.me.uk/lib/LTO/ThinLTOCodeGenerator.cpp#763
> Right now we apply internalization despite the warning
> because ExportList.size() is equal to 3 at that point. I think what might
> be happening for you is that your change causes ExportList.size() to become
> 0, so we don't actually internalize anything. Presumably the 3 symbols are
> the linkonce aliases but I don't have time to confirm that.
>
>
>>>
>>>> It looks like if I fix this by passing -exported-symbol=main, nothing
>>>>> is internalized (all the aliases are called from main) so it may defeat the
>>>>> purpose of this test?
>>>>>
>>>>
>>>> Right, if we export main then that would prevent us from internalizing
>>>> anything across modules that is referenced by main, as we don't currently
>>>> support cross-module internalization.
>>>>
>>>
>>> Not sure I follow that - it seemed to work (in the sense that saying
>>> main was exported, nothing was internalized - which seems like the correct
>>> answer to me, rather than "unsupported" (though unsupported could mean it
>>> does that but breaks elsewhere - fair enough))
>>>
>>>
>>>> (I don't really understand how this was working/what it was doing
>>>>> before, though: What kept the aliasees alive if not the calls from main?
>>>>> Maybe a record in the index saying "these are being used elsewhere" - but
>>>>> why isn't there a similar record for the aliases that would've stopped them
>>>>> from being internalized in the first place?)
>>>>>
>>>>
>>>> I don't recall for sure but I believe that the point of that part of
>>>> the test was to show that if no symbols are exported, the linkage changes
>>>> applied by promote are unimportant because they are wiped out by a later
>>>> internalize pass (which would internalize pretty much everything because
>>>> nothing is exported).
>>>>
>>>
>>> Except there are exported symbols... - if there are no exported symbols
>>> then internalize doesn't run so it wouldn't show/demonstrate anything?
>>>
>>
> The symbols currently being exported are linkonce/weak so they presumably
> end up in ExportList regardless of what flags you pass in.
>
>>
>> aside: It looked like the behavior was incorrect anyway: It internalized
>> the aliases which were actually called cross-module, but it /didn't/
>> internalize the things that were cross-modular imported... - it looks like
>> it did exactly the opposite of what would be desired?
>>
>
> That's certainly possible, although I suspect it is more likely an
> artifact of how llvm-lto works (which I find super confusing -- one of the
> reasons why I designed llvm-lto2 to use the same sequence of ThinLTO
> "passes" as production links).
>
> Peter
>
>>
>>
>>>
>>>
>>>> So I think the right change to make in that part of the test (if we
>>>> wanted to go with your proposed change) would be to test that the remaining
>>>> declarations are internal.
>>>>
>>>> Peter
>>>>
>>>>
>>>>> Preciate any thoughts you have here,
>>>>>
>>>>> - Dave
>>>>>
>>>>>
>>>>> On Wed, Jul 6, 2016 at 4:00 PM Peter Collingbourne via llvm-commits <
>>>>> llvm-commits at lists.llvm.org> wrote:
>>>>>
>>>>>> Author: pcc
>>>>>> Date: Wed Jul  6 17:53:02 2016
>>>>>> New Revision: 274699
>>>>>>
>>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=274699&view=rev
>>>>>> Log:
>>>>>> ThinLTO: Add test cases for promote+internalize.
>>>>>>
>>>>>> This tests the effect of both promotion and internalization on a
>>>>>> module,
>>>>>> and helps show that D21883 is NFC wrt promotion+internalization.
>>>>>>
>>>>>> Differential Revision: http://reviews.llvm.org/D21915
>>>>>>
>>>>>> Modified:
>>>>>>     llvm/trunk/test/ThinLTO/X86/alias_import.ll
>>>>>>     llvm/trunk/test/ThinLTO/X86/weak_resolution.ll
>>>>>>
>>>>>> Modified: llvm/trunk/test/ThinLTO/X86/alias_import.ll
>>>>>> URL:
>>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/ThinLTO/X86/alias_import.ll?rev=274699&r1=274698&r2=274699&view=diff
>>>>>>
>>>>>> ==============================================================================
>>>>>> --- llvm/trunk/test/ThinLTO/X86/alias_import.ll (original)
>>>>>> +++ llvm/trunk/test/ThinLTO/X86/alias_import.ll Wed Jul  6 17:53:02
>>>>>> 2016
>>>>>> @@ -2,6 +2,7 @@
>>>>>>  ; RUN: opt -module-summary %p/Inputs/alias_import.ll -o %t2.bc
>>>>>>  ; RUN: llvm-lto -thinlto-action=thinlink -o %t.index.bc %t1.bc %t2.bc
>>>>>>  ; RUN: llvm-lto -thinlto-action=promote -thinlto-index %t.index.bc
>>>>>> %t2.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=PROMOTE
>>>>>> +; RUN: llvm-lto -thinlto-action=promote -thinlto-index %t.index.bc
>>>>>> %t2.bc -o - | llvm-lto -thinlto-action=internalize -thinlto-index
>>>>>> %t.index.bc -thinlto-module-id=%t2.bc - -o - | llvm-dis -o - | FileCheck %s
>>>>>> --check-prefix=PROMOTE-INTERNALIZE
>>>>>>  ; RUN: llvm-lto -thinlto-action=import -thinlto-index %t.index.bc
>>>>>> %t1.bc -o - | llvm-dis -o - | FileCheck %s --check-prefix=IMPORT
>>>>>>
>>>>>>  ;
>>>>>> @@ -86,7 +87,45 @@
>>>>>>  ; IMPORT-DAG: declare void @weakfuncWeakODRAlias()
>>>>>>  ; IMPORT-DAG: declare void @weakfuncLinkonceODRAlias()
>>>>>>
>>>>>> -
>>>>>> +; Promotion + internalization should internalize all of these,
>>>>>> except for aliases of
>>>>>> +; linkonce_odr functions, because alias to linkonce_odr are the only
>>>>>> aliases we will
>>>>>> +; import (see selectCallee() in FunctionImport.cpp).
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncAlias = internal alias void
>>>>>> (...), bitcast (void ()* @globalfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncWeakAlias = internal alias
>>>>>> void (...), bitcast (void ()* @globalfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncLinkonceAlias = internal alias
>>>>>> void (...), bitcast (void ()* @globalfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncWeakODRAlias = internal alias
>>>>>> void (...), bitcast (void ()* @globalfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @globalfuncLinkonceODRAlias = internal
>>>>>> alias void (...), bitcast (void ()* @globalfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncAlias = internal alias void
>>>>>> (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncWeakAlias = internal alias
>>>>>> void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncLinkonceAlias = internal
>>>>>> alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncWeakODRAlias = internal
>>>>>> alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @internalfuncLinkonceODRAlias = internal
>>>>>> alias void (...), bitcast (void ()* @internalfunc.llvm.0 to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncAlias = alias void (...),
>>>>>> bitcast (void ()* @linkonceODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncWeakAlias = internal
>>>>>> alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncLinkonceAlias = internal
>>>>>> alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncWeakODRAlias = weak_odr
>>>>>> alias void (...), bitcast (void ()* @linkonceODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkonceODRfuncLinkonceODRAlias =
>>>>>> weak_odr alias void (...), bitcast (void ()* @linkonceODRfunc to void
>>>>>> (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncAlias = internal alias void
>>>>>> (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncWeakAlias = internal alias
>>>>>> void (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncLinkonceAlias = internal
>>>>>> alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncWeakODRAlias = internal alias
>>>>>> void (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakODRfuncLinkonceODRAlias = internal
>>>>>> alias void (...), bitcast (void ()* @weakODRfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncAlias = internal alias void
>>>>>> (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncWeakAlias = internal alias
>>>>>> void (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncLinkonceAlias = internal
>>>>>> alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncWeakODRAlias = internal
>>>>>> alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @linkoncefuncLinkonceODRAlias = internal
>>>>>> alias void (...), bitcast (void ()* @linkoncefunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncAlias = internal alias void
>>>>>> (...), bitcast (void ()* @weakfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncWeakAlias = internal alias void
>>>>>> (...), bitcast (void ()* @weakfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncLinkonceAlias = internal alias
>>>>>> void (...), bitcast (void ()* @weakfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncWeakODRAlias = internal alias
>>>>>> void (...), bitcast (void ()* @weakfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: @weakfuncLinkonceODRAlias = internal
>>>>>> alias void (...), bitcast (void ()* @weakfunc to void (...)*)
>>>>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @globalfunc()
>>>>>> +; PROMOTE-INTERNALIZE-DAG: define internal void
>>>>>> @internalfunc.llvm.0()
>>>>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @linkonceODRfunc()
>>>>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @weakODRfunc()
>>>>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @linkoncefunc()
>>>>>> +; PROMOTE-INTERNALIZE-DAG: define internal void @weakfunc()
>>>>>>
>>>>>>  define i32 @main() #0 {
>>>>>>  entry:
>>>>>>
>>>>>> Modified: llvm/trunk/test/ThinLTO/X86/weak_resolution.ll
>>>>>> URL:
>>>>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/ThinLTO/X86/weak_resolution.ll?rev=274699&r1=274698&r2=274699&view=diff
>>>>>>
>>>>>> ==============================================================================
>>>>>> --- llvm/trunk/test/ThinLTO/X86/weak_resolution.ll (original)
>>>>>> +++ llvm/trunk/test/ThinLTO/X86/weak_resolution.ll Wed Jul  6
>>>>>> 17:53:02 2016
>>>>>> @@ -7,6 +7,7 @@
>>>>>>  ; non-prevailing ODR are not kept when possible, but non-ODR
>>>>>> non-prevailing
>>>>>>  ; are not affected.
>>>>>>  ; RUN: llvm-lto -thinlto-action=promote %t.bc -thinlto-index=%t3.bc
>>>>>> -o - | llvm-dis -o - | FileCheck %s --check-prefix=MOD1
>>>>>> +; RUN: llvm-lto -thinlto-action=promote %t.bc -thinlto-index=%t3.bc
>>>>>> -exported-symbol=linkoncefunc -o - | llvm-lto -thinlto-action=internalize
>>>>>> -thinlto-module-id=%t.bc - -thinlto-index=%t3.bc
>>>>>> -exported-symbol=linkoncefunc -o - | llvm-dis -o - | FileCheck %s
>>>>>> --check-prefix=MOD1-INT
>>>>>>  ; RUN: llvm-lto -thinlto-action=promote %t2.bc -thinlto-index=%t3.bc
>>>>>> -o - | llvm-dis -o - | FileCheck %s --check-prefix=MOD2
>>>>>>  ; When exported, we always preserve a linkonce
>>>>>>  ; RUN: llvm-lto -thinlto-action=promote %t.bc -thinlto-index=%t3.bc
>>>>>> -o - --exported-symbol=linkonceodrfuncInSingleModule | llvm-dis -o - |
>>>>>> FileCheck %s --check-prefix=EXPORTED
>>>>>> @@ -47,6 +48,7 @@ entry:
>>>>>>    ret void
>>>>>>  }
>>>>>>  ; MOD1: define weak void @linkoncefunc()
>>>>>> +; MOD1-INT: define weak void @linkoncefunc()
>>>>>>  ; MOD2: define linkonce void @linkoncefunc()
>>>>>>  define linkonce void @linkoncefunc() #0 {
>>>>>>  entry:
>>>>>> @@ -66,6 +68,7 @@ entry:
>>>>>>  }
>>>>>>
>>>>>>  ; MOD1: define linkonce_odr void @linkonceodrfuncInSingleModule()
>>>>>> +; MOD1-INT: define internal void @linkonceodrfuncInSingleModule()
>>>>>>  ; EXPORTED: define weak_odr void @linkonceodrfuncInSingleModule()
>>>>>>  define linkonce_odr void @linkonceodrfuncInSingleModule() #0 {
>>>>>>  entry:
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> llvm-commits mailing list
>>>>>> llvm-commits at lists.llvm.org
>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> --
>>>> Peter
>>>>
>>>
>
>
> --
> --
> Peter
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170726/8fb89a1d/attachment.html>