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

Tue Jul 25 17:52:10 PDT 2017

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.
>
>
>> 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?
>

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?

>
>
>> 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
>>
>
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