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

Mon Feb 8 15:58:10 PST 2016

To be clear, you are suggesting breaking the test into two (one for
copy, and one for move) ? I am totally fine with that.  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.

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
>> >> >> >>
>> >> >> >
>> >> >
>> >> >
>> >
>> >
>
>