[PATCH] D16947: [PGO] assignment operator does not get profile data

Mon Feb 8 17:23:38 PST 2016

On Mon, Feb 8, 2016 at 5:05 PM, Xinliang David Li <davidxl at google.com>
wrote:

> ha! somehow I kept thinking you are referring to implicit declared ctors.
>

Ah, glad we figured out the disconnect - thanks for bearing with me!

>
> From your test case, it is seems that the implicit copy/move op is
> also broken and is fixed by this patch too. That means  a missing test
> case to me.  Will update the case when verified.
>

Again, this is a case where I'd probably just simplify the test, as I asked
earlier in the thread (I asked if it mattered if the op was explicitly or
implicitly defaulted (& your response: "> Is the fix/codepath specifically
about explicitly defaulted ops?

yes -- explicitly defaulted. There are some test coverage already for
implicitly declared ctors (but not assignment op -- probably worth
adding some testing too).")

So I'd just simplify the test by removing the "= default" - I don't think
there's value in testing both the explicit default and implicit default if
it's just the default-y-ness that's relevant here. Otherwise we could end
up testing all sorts of ways of writing/interacting with dtors which
wouldn't be relevant to the code/fix/etc.

This seems like the obvious test for the behavior:

struct foo {
  // non-trivial ops
  foo &operator=(const foo&);
  foo &operator=(foo&&);
};

struct bar {
  foo f; // or derive bar from foo, but I think the member version is
simpler
};

// force emission of bar's implicit special members, one way or another:
bar &(bar::*x)(const bar&) = &bar::operator=;
bar &(bar::*x)(bar&&) = &bar::operator=;

(or just call them as you had in your test case - but that produces more
code, etc in the module, extra functions/profile counters/etc)

- Dave

>
> thanks,
>
> David
>
>
> On Mon, Feb 8, 2016 at 4:58 PM, David Blaikie <dblaikie at gmail.com> wrote:
> >
> >
> > On Mon, Feb 8, 2016 at 4:31 PM, Xinliang David Li <davidxl at google.com>
> > wrote:
> >>
> >> On Mon, Feb 8, 2016 at 4:05 PM, David Blaikie <dblaikie at gmail.com>
> wrote:
> >> >
> >> >
> >> > On Mon, Feb 8, 2016 at 3:58 PM, Xinliang David Li <davidxl at google.com
> >
> >> > wrote:
> >> >>
> >> >> To be clear, you are suggesting breaking the test into two (one for
> >> >> copy, and one for move) ? I am totally fine with that.
> >> >
> >> >
> >> > Nah, no need to split the test case - we try to keep the number of
> test
> >> > files down (& group related tests into a single file) to reduce test
> >> > execution time (a non-trivial about of check time is spent in process
> >> > overhead).
> >> >
> >> >>
> >> >>   I thought you
> >> >> suggested removing the testing of move/op case because they might
> >> >> share the same code path (clang's implementation) as the copy/op.
> >> >
> >> >
> >> > I was suggesting that two cases is no big deal whether you test both
> or
> >> > test
> >> > one if they're the same codepath - if there were 5/many more things
> that
> >> > shared the same codepath, I'd generally suggest testing a
> representative
> >> > sample (possibly just a single one) rather than testing every client
> of
> >> > the
> >> > same code.
> >> >
> >> > Feel free to leave the two here as-is. (though if we're talking about
> >> > test
> >> > granularity, it's probably worth just putting these cases in the same
> >> > file/type/etc as the ctor cases you mentioned were already covered)
> >>
> >> There is a balance somewhere:
> >> 1) for small test cases like this, the overhead mainly comes from test
> >> set up cost -- adding additional incremental test in the same file
> >> probably almost comes for free (in terms of cost). However
> >> 2) having too many cases grouped together also reduces the
> >> debuggability when some test fails.
> >
> >
> > Yep, for sure. In this case, testing the ctors and assignment ops in one
> > file's probably not a bad tradeoff (you can see how Clang groups its
> tests -
> > a file per language feature in many cases, exploring the myriad ways the
> > feature can be used - this doesn't always work spectacularly (when you
> can't
> > order the IR emission to happen mostly in the order that the source is
> > written (rather being interleaved))
> >
> > Anyway, up to you - that part isn't something I'm terribly worried about
> > either way.
> >
> >>
> >>
> >> >
> >> > & I'm still curious/wondering if there's a common codepath that would
> >> > provide a simpler fix/code that solved both implicit and explicitly
> >> > defaulted ops.
> >>
> >> I may take a look at that when I find time -- but there is no guarantee
> :)
> >
> >
> > A quick test of putting "assert(false)" in
> > emitImplicitAssignmentOperatorBody and running Clang over this code:
> >
> > struct foo {
> >   foo &operator=(const foo &);
> > };
> >
> > struct bar {
> >   foo f;
> > };
> >
> > auto (bar::*x)(const bar&) = &bar::operator=;
> >
> > Fires the assertion - this seems to me to indicate that the codepath you
> > changed is used for both the explicitly (based on the change fixing your
> > test case) and implicitly defaulted (based on my test case) cases.
> >
> > Is it possible that you end up with duplicate counters by accident in
> this
> > path, then? Or at least that whatever codepath was handling the
> implicitly
> > defaulted ones is now redundant with this one?
> >
> > Actually, so far as I can tell this doesn't work for implicitly defaulted
> > move ops (the above test case doesn't have an add pgocount in it) -
> perhaps
> > I'm missing something/doing it wrong? or was just not communicating
> clearly
> > regarding explicit versus implicitly defaulted special members.
> >
> > - Dave
> >
> >>
> >>
> >> thanks,
> >>
> >> David
> >>
> >>
> >>
> >> >
> >> > - Dave
> >> >
> >> >>
> >> >>
> >> >> thanks,
> >> >>
> >> >> David
> >> >>
> >> >> On Mon, Feb 8, 2016 at 3:52 PM, David Blaikie <dblaikie at gmail.com>
> >> >> wrote:
> >> >> >
> >> >> >
> >> >> > On Mon, Feb 8, 2016 at 3:46 PM, Xinliang David Li
> >> >> > <davidxl at google.com>
> >> >> > wrote:
> >> >> >>
> >> >> >> On Mon, Feb 8, 2016 at 3:35 PM, David Blaikie <dblaikie at gmail.com
> >
> >> >> >> wrote:
> >> >> >> >
> >> >> >> >
> >> >> >> > On Mon, Feb 8, 2016 at 3:21 PM, Xinliang David Li
> >> >> >> > <davidxl at google.com>
> >> >> >> > wrote:
> >> >> >> >>
> >> >> >> >> On Mon, Feb 8, 2016 at 3:17 PM, David Blaikie
> >> >> >> >> <dblaikie at gmail.com>
> >> >> >> >> wrote:
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > On Mon, Feb 8, 2016 at 12:07 PM, Xinliang David Li
> >> >> >> >> > <davidxl at google.com>
> >> >> >> >> > wrote:
> >> >> >> >> >>
> >> >> >> >> >> On Mon, Feb 8, 2016 at 11:39 AM, David Blaikie
> >> >> >> >> >> <dblaikie at gmail.com>
> >> >> >> >> >> wrote:
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> > On Mon, Feb 8, 2016 at 9:25 AM, David Li via llvm-commits
> >> >> >> >> >> > <llvm-commits at lists.llvm.org> wrote:
> >> >> >> >> >> >>
> >> >> >> >> >> >> davidxl updated this revision to Diff 47217.
> >> >> >> >> >> >> davidxl added a comment.
> >> >> >> >> >> >>
> >> >> >> >> >> >> Simplified test case suggested by Vedant.
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >> http://reviews.llvm.org/D16947
> >> >> >> >> >> >>
> >> >> >> >> >> >> Files:
> >> >> >> >> >> >>   lib/CodeGen/CGClass.cpp
> >> >> >> >> >> >>   test/Profile/def-assignop.cpp
> >> >> >> >> >> >>
> >> >> >> >> >> >> Index: test/Profile/def-assignop.cpp
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> ===================================================================
> >> >> >> >> >> >> --- test/Profile/def-assignop.cpp
> >> >> >> >> >> >> +++ test/Profile/def-assignop.cpp
> >> >> >> >> >> >> @@ -0,0 +1,32 @@
> >> >> >> >> >> >> +// RUN: %clang_cc1 -x c++ -std=c++11 %s -triple
> >> >> >> >> >> >> x86_64-unknown-linux-gnu
> >> >> >> >> >> >> -main-file-name def-assignop.cpp -o - -emit-llvm
> >> >> >> >> >> >> -fprofile-instrument=clang
> >> >> >> >> >> >> | FileCheck --check-prefix=PGOGEN %s
> >> >> >> >> >> >> +// RUN: %clang_cc1 -x c++ -std=c++11 %s -triple
> >> >> >> >> >> >> x86_64-unknown-linux-gnu
> >> >> >> >> >> >> -main-file-name def-assignop.cpp -o - -emit-llvm
> >> >> >> >> >> >> -fprofile-instrument=clang
> >> >> >> >> >> >> -fcoverage-mapping | FileCheck --check-prefix=COVMAP %s
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +struct B {
> >> >> >> >> >> >> +  void operator=(const B &b) {}
> >> >> >> >> >> >> +  void operator=(const B &&b) {}
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> > Probably best to make these canonical to avoid confusion:
> >> >> >> >> >> >
> >> >> >> >> >> > B &operator=(const B&);
> >> >> >> >> >> > B &operator=(B&&);
> >> >> >> >> >> >
> >> >> >> >> >> > (& they don't need definitions - just declarations)
> >> >> >> >> >>
> >> >> >> >> >> Will change.
> >> >> >> >> >>
> >> >> >> >> >> >
> >> >> >> >> >> > Also, neither of these are the move /constructor/, just
> the
> >> >> >> >> >> > move
> >> >> >> >> >> > operator.
> >> >> >> >> >> > Not sure if Vedant just used the wrong terminology, or
> >> >> >> >> >> > whether
> >> >> >> >> >> > it's
> >> >> >> >> >> > worth
> >> >> >> >> >> > testing the move/copy ctors too, to check that they do the
> >> >> >> >> >> > right
> >> >> >> >> >> > thing
> >> >> >> >> >> > as
> >> >> >> >> >>
> >> >> >> >> >> I added tests for copy ctors, and plan to add move ctor test
> >> >> >> >> >> soon.
> >> >> >> >> >>
> >> >> >> >> >> > well. (if all of these things use the same codepath, I
> don't
> >> >> >> >> >> > see a
> >> >> >> >> >> > great
> >> >> >> >> >> > benefit in having separate tests for them (but you can add
> >> >> >> >> >> > them
> >> >> >> >> >> > here
> >> >> >> >> >> > if
> >> >> >> >> >> > you
> >> >> >> >> >> > like) - I'm just suggesting a manual verification in case
> >> >> >> >> >> > those
> >> >> >> >> >> > need
> >> >> >> >> >> > a
> >> >> >> >> >> > separate fix
> >> >> >> >> >>
> >> >> >> >> >> the ctor and assignment op do not share the same path -- the
> >> >> >> >> >> ctor
> >> >> >> >> >> path
> >> >> >> >> >> is working as expected without the fix -- or do you mean
> there
> >> >> >> >> >> is
> >> >> >> >> >> no
> >> >> >> >> >> need to cover both copy and move variants?
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > I wouldn't necessarily bother testing multiple instances of
> the
> >> >> >> >> > same
> >> >> >> >> > codepath (so the copy and move ctor for example) - but 2
> >> >> >> >> > instances
> >> >> >> >> > is
> >> >> >> >> > no
> >> >> >> >> > big
> >> >> >> >> > deal (if there were several more, I might be inclined to just
> >> >> >> >> > test
> >> >> >> >> > one
> >> >> >> >> > as a
> >> >> >> >> > representative sample). I don't mind either way, though. The
> >> >> >> >> > number
> >> >> >> >> > is
> >> >> >> >> > small
> >> >> >> >> > & the test cases are arguably distinct.
> >> >> >> >>
> >> >> >> >> Sorry I disagree with your general statement here. I treat such
> >> >> >> >> test
> >> >> >> >> cases as 'black box testing' that do not know about the
> internal
> >> >> >> >> implementation (code path). It may or may not share the same
> code
> >> >> >> >> path
> >> >> >> >> today -- same is true in the future.
> >> >> >> >
> >> >> >> >
> >> >> >> > While there's merit in both approaches, practically speaking it
> >> >> >> > seems
> >> >> >> > difficult to test in that way in general - any feature could
> >> >> >> > interact
> >> >> >> > with
> >> >> >> > any other.
> >> >> >>
> >> >> >> The language features are well specified -- so writing small test
> >> >> >> cases to cover them is a general accepted way of testing.
> >> >> >
> >> >> >
> >> >> > I'm not sure I follow the distinction you're drawing between the
> >> >> > middle
> >> >> > end
> >> >> > optimization tests and the features you're testing here. If the
> >> >> > features
> >> >> > are
> >> >> > relatively independent, even within the same API/feature area,
> >> >> > they're
> >> >> > generally tested independently (even two features within a single
> >> >> > middle
> >> >> > end
> >> >> > optimization - a test case is written to ensure that, say,
> >> >> > ArgumentPromotion
> >> >> > correctly handles debug info, and another that it correctly handles
> >> >> > inalloca
> >> >> > (or fp80, etc - just looking at test/Transforms/ArgumentPromotion)
> -
> >> >> > but
> >> >> > we
> >> >> > don't test the matrix of combinations of these features)
> >> >> >
> >> >> >>
> >> >> >>
> >> >> >> >The LLVM regression suite is far more narrowly targeted than that
> >> >> >> > - we don't test combinations of optimizations, for example - we
> >> >> >> > test
> >> >> >> > each
> >> >> >> > optimization in isolation. The same would be true of two
> >> >> >> > independent
> >> >> >> > features on an interface such as this, I think.
> >> >> >>
> >> >> >> This is a weakness of the test system -- a problem at a different
> >> >> >> dimension.
> >> >> >
> >> >> >
> >> >> > If we want to have a discussion about the LLVM community testing
> >> >> > methodology, that might be best taken up on llvm-dev (and
> clang-dev).
> >> >> > But
> >> >> > for now, I'd ask that tests in the lit regression suite are
> generally
> >> >> > as
> >> >> > isolated as possible and test one thing at a time.
> >> >> >
> >> >> >>
> >> >> >>
> >> >> >> >
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >> >
> >> >> >> >> >> >>
> >> >> >> >> >> >> +};
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +struct A {
> >> >> >> >> >> >> +  A &operator=(const A &) = default;
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> > Is the fix/codepath specifically about explicitly
> defaulted
> >> >> >> >> >> > ops?
> >> >> >> >> >>
> >> >> >> >> >> yes -- explicitly defaulted. There are some test coverage
> >> >> >> >> >> already
> >> >> >> >> >> for
> >> >> >> >> >> implicitly declared ctors (but not assignment op -- probably
> >> >> >> >> >> worth
> >> >> >> >> >> adding some testing too).
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> > Hmm - are you sure there's no common codepath that would
> cover
> >> >> >> >> > the
> >> >> >> >> > explicitly defaulted or implicitly defaulted ops together in
> >> >> >> >> > one
> >> >> >> >> > go?
> >> >> >> >>
> >> >> >> >> Sorry I am not sure what you mean here.
> >> >> >> > Is there some part of Clang that is responsible for generating
> >> >> >> > both
> >> >> >> > implicitly defaulted and explicitly defaulted move/copy ops that
> >> >> >> > could
> >> >> >> > handle this case, rather than apparently handling the implicit
> and
> >> >> >> > explicit
> >> >> >> > cases separately (it seems they're being handled separately if
> the
> >> >> >> > implicit
> >> >> >> > case worked before and you added code (rather than moving code)
> to
> >> >> >> > fix
> >> >> >> > the
> >> >> >> > explicit case - it sounds like we now have two bits of code, one
> >> >> >> > for
> >> >> >> > implicit and one for explicit - perhaps there's a single bit of
> >> >> >> > code
> >> >> >> > that we
> >> >> >> > could write that would handle both?)
> >> >> >>
> >> >> >> The codegen paths are different -- otherwise as you commented, the
> >> >> >> implicit case would have been broken too.
> >> >> >>
> >> >> >> Refactoring FE code to handle both is probably beyond the scope of
> >> >> >> this fix.  Having a good test case here will exactly help avoid
> >> >> >> regression if that happens in the future.
> >> >> >>
> >> >> >> David
> >> >> >>
> >> >> >> >
> >> >> >> > - David
> >> >> >> >
> >> >> >> >>
> >> >> >> >>
> >> >> >> >> David
> >> >> >> >>
> >> >> >> >> >
> >> >> >> >> >>
> >> >> >> >> >>
> >> >> >> >> >> > Or just any
> >> >> >> >> >> > compiler-generated ones? (you could drop these lines if
> it's
> >> >> >> >> >> > about
> >> >> >> >> >> > any
> >> >> >> >> >> > compiler-generated ones, might be simpler/more obvious
> that
> >> >> >> >> >> > it's
> >> >> >> >> >> > not
> >> >> >> >> >> > about
> >> >> >> >> >> > the "= default" feature)
> >> >> >> >> >>
> >> >> >> >> >> Other compiler generated ones are handled differently.
> >> >> >> >> >>
> >> >> >> >> >> thanks,
> >> >> >> >> >>
> >> >> >> >> >> David
> >> >> >> >> >>
> >> >> >> >> >> >
> >> >> >> >> >> >>
> >> >> >> >> >> >> +  // PGOGEN: define {{.*}}@_ZN1AaSERKS_(
> >> >> >> >> >> >> +  // PGOGEN: %pgocount = load {{.*}}
> @__profc__ZN1AaSERKS_
> >> >> >> >> >> >> +  // PGOGEN: {{.*}}add{{.*}}%pgocount, 1
> >> >> >> >> >> >> +  // PGOGEN: store{{.*}}@__profc__ZN1AaSERKS_
> >> >> >> >> >> >> +  A &operator=(A &&) = default;
> >> >> >> >> >> >>
> >> >> >> >> >> >> +  // PGOGEN: define {{.*}}@_ZN1AaSEOS_
> >> >> >> >> >> >> +  // PGOGEN: %pgocount = load {{.*}}
> @__profc__ZN1AaSEOS_
> >> >> >> >> >> >> +  // PGOGEN: {{.*}}add{{.*}}%pgocount, 1
> >> >> >> >> >> >> +  // PGOGEN: store{{.*}}@__profc__ZN1AaSEOS_
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +  // Check that coverage mapping includes 6 function
> >> >> >> >> >> >> records
> >> >> >> >> >> >> including
> >> >> >> >> >> >> the
> >> >> >> >> >> >> +  // defaulted copy and move operators: A::operator=
> >> >> >> >> >> >> +  // COVMAP: @__llvm_coverage_mapping = {{.*}} { { i32,
> >> >> >> >> >> >> i32,
> >> >> >> >> >> >> i32,
> >> >> >> >> >> >> i32
> >> >> >> >> >> >> },
> >> >> >> >> >> >> [5 x <{{.*}}>],
> >> >> >> >> >> >> +  B b;
> >> >> >> >> >> >> +};
> >> >> >> >> >> >> +
> >> >> >> >> >> >> +int main() {
> >> >> >> >> >> >> +  A a1, a2;
> >> >> >> >> >> >> +  a1 = a2;
> >> >> >> >> >> >> +  a2 = static_cast<A &&>(a1);
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> > An option, though not necessarily better, would be to just
> >> >> >> >> >> > take
> >> >> >> >> >> > the
> >> >> >> >> >> > address
> >> >> >> >> >> > of the special members:
> >> >> >> >> >> >
> >> >> >> >> >> > auto (B::*x)(const B&) = &bar::operator=;
> >> >> >> >> >> > auto (B::*x)(B&&) = &bar::operator=;
> >> >> >> >> >> >
> >> >> >> >> >> > In short, what I'm picturing, in total:
> >> >> >> >> >> >
> >> >> >> >> >> > struct A {
> >> >> >> >> >> >   A &operator=(const A&);
> >> >> >> >> >> >   A &operator=(A&&);
> >> >> >> >> >> > };
> >> >> >> >> >> >
> >> >> >> >> >> > struct B {
> >> >> >> >> >> >   A a;
> >> >> >> >> >> > };
> >> >> >> >> >> >
> >> >> >> >> >> > auto (B::*x)(const B&) = &B::operator=;
> >> >> >> >> >> > auto (B::*x)(B&&) = &B::operator=;
> >> >> >> >> >> >
> >> >> >> >> >> > Also, this test should probably be in clang, since it's a
> >> >> >> >> >> > clang
> >> >> >> >> >> > code
> >> >> >> >> >> > change/fix.
> >> >> >> >> >> >
> >> >> >> >> >> >
> >> >> >> >> >> >>
> >> >> >> >> >> >> +  return 0;
> >> >> >> >> >> >> +}
> >> >> >> >> >> >> Index: lib/CodeGen/CGClass.cpp
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> ===================================================================
> >> >> >> >> >> >> --- lib/CodeGen/CGClass.cpp
> >> >> >> >> >> >> +++ lib/CodeGen/CGClass.cpp
> >> >> >> >> >> >> @@ -1608,6 +1608,7 @@
> >> >> >> >> >> >>
> >> >> >> >> >> >>    LexicalScope Scope(*this, RootCS->getSourceRange());
> >> >> >> >> >> >>
> >> >> >> >> >> >> +  incrementProfileCounter(RootCS);
> >> >> >> >> >> >>    AssignmentMemcpyizer AM(*this, AssignOp, Args);
> >> >> >> >> >> >>    for (auto *I : RootCS->body())
> >> >> >> >> >> >>      AM.emitAssignment(I);
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >>
> >> >> >> >> >> >> _______________________________________________
> >> >> >> >> >> >> llvm-commits mailing list
> >> >> >> >> >> >> llvm-commits at lists.llvm.org
> >> >> >> >> >> >>
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
> >> >> >> >> >> >>
> >> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >> >
> >> >> >> >
> >> >> >> >
> >> >> >
> >> >> >
> >> >
> >> >
> >
> >
>
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