hoy added inline comments.
================
Comment at: clang/test/CodeGen/unique-internal-linkage-names.cpp:48-49
+// LPIPELINE: Unique Internal Linkage Names
+// NPIPELINE: Running pass: UniqueInternalLinkageNamesPass
// PLAIN: @_ZL4glob = internal global
----------------
aeubanks wrote:
> dblaikie wrote:
> > hoy wrote:
> > > dblaikie wrote:
> > > > Does this test validate the new behavior? (ie: does this test fail
> > > > without the LLVM changes and pass with it) Not that it necessarily has
> > > > to - since Clang isn't here to test the LLVM behavior - perhaps this
> > > > test is sufficient in Clang to test that the code in BackendUtil works
> > > > to enable this pass.
> > > >
> > > > This could possibly be staged as independent commits - adding the LLVM
> > > > functionality in one commit, which would be a no-op for Clang because
> > > > it wouldn't be setting PTO.UniqueLinkageNames - then committing the
> > > > Clang change that would remove the custom pass addition and set
> > > > PTO.UniqueLinkageNames - and then it'd probably be reasonable to have
> > > > this test be made a bit more explicit (testing the pass manager
> > > > structure/order) to show that that Clang change had an effect: Moving
> > > > the pass to the desired location in the pass pipeline.
> > > This is a good question. No, this test does not validate the pipeline
> > > change on the LLVM side, since Clang shouldn't have knowledge about how
> > > the pipelines are arranged in LLVM. As you pointed out, the test here is
> > > to test if the specific pass is run and gives expected results.
> > >
> > > Thanks for the suggestion to break the Clang changes and LLVM changes
> > > apart which would make the testing more specific. The pipeline ordering
> > > could be tested with a LLVM test but that would require a LLVM switch
> > > setup for UniqueLinkageNames and I'm not sure there's a need for that
> > > switch except for testing.
> > > No, this test does not validate the pipeline change on the LLVM side,
> > > since Clang shouldn't have knowledge about how the pipelines are arranged
> > > in LLVM.
> >
> > "ish" - but Clang should have tests for changes to Clang, ideally. Usually
> > they can simply be testing LLVM's IR output before it goes to LLVM for
> > optimization/codegen - but for features that don't have this serialization
> > boundary that makes testing and isolation clear/simple, it becomes a bit
> > fuzzier.
> >
> > In this case, there is a clang change - from adding the pass explicitly in
> > Clang, to setting a parameter about how LLVM will add the pass, and it has
> > an observable effect. One way to test this change while isolating the Clang
> > test from further changes to the pipeline in LLVM, would be to test that
> > the pass ends up somewhere in the LLVM-created part of the pass pipeline -
> > the parts that you can't get to from the way the original pass addition was
> > written in Clang. At least I assume that's the case/what motivated the
> > change from adding it in Clang to adding it in LLVM?
> >
> > eg: if LLVM always forms passes {x, y, z} and Clang is able to add passes
> > before/after, say it always adds 'a' before and 'b' after, to make {a, x,
> > y, z, b} - and this new pass u was previously added at the start to make
> > {u, a, x, y, z, b} but now needs to go in {a, x, y, u, z, b} you could test
> > that 'u' is after 'a' and before 'b', or between 'x' and 'z', etc. If
> > there's some other more clear/simple/reliable marker of where the
> > LLVM-created passes start/end in the structured dump, that'd be good to use
> > as a landmark to make such a test more robust. If there's some meaningful
> > pass that this pass always needs to go after - testing that might be OK,
> > even if it's somewhat an implementation detail of LLVM - whatever's likely
> > to make the test more legible and more reliable/resilient to unrelated
> > changes would be good.
> >
> > > As you pointed out, the test here is to test if the specific pass is run
> > > and gives expected results.
> >
> > If that's the case, this test could be committed standalone, before any of
> > these other changes?
> >
> > > The pipeline ordering could be tested with a LLVM test but that would
> > > require a LLVM switch setup for UniqueLinkageNames and I'm not sure
> > > there's a need for that switch except for testing.
> >
> > That's OK, the entire 'opt' tool and all its switches only exist for
> > testing. eg:
> > https://github.com/llvm/llvm-project/blob/master/llvm/tools/opt/NewPMDriver.cpp#L284
> The point of this change is that UniqueInternalLinkageNamesPass should run
> before SampleProfileProbePass. That must make a difference in the output of
> something like `clang -emit-llvm -O1`, right? Maybe we can add a new clang
> test that checks for that new change in IR, no need to check
> -fdebug-pass-manager. (I'm not familiar with the passes, correct me if I'm
> wrong)
Maybe we can just keep the Clang test unchanged? What do you think? Since it's
basically testing the command line switch `-funique-internal-linkage-names`
works as expected, i.e, giving unique linkage names, it probably shouldn't care
where the renaming happens exactly. Checking the pass order sounds a job to
LLVM. I'll make the LLVM test do that.
> The point of this change is that UniqueInternalLinkageNamesPass should run
> before SampleProfileProbePass.
Yeah, that's the point. We should probably make an LLVM test for it instead of
a Clang test.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D93656/new/
https://reviews.llvm.org/D93656
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