llvm dev - Feb 2016 - [cfe-dev] Testing Best Practices/Goals (in the context of compiler-rt)

On Fri, Feb 26, 2016 at 1:07 PM, Sean Silva <chisophugis at gmail.com>
wrote:
>
>
> On Wed, Feb 17, 2016 at 8:45 AM, David Blaikie via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>>
>>
>> On Fri, Feb 12, 2016 at 5:43 PM, Alexey Samsonov <vonosmas at
gmail.com>
>> wrote:
>>
>>>
>>>
>>> On Thu, Feb 11, 2016 at 1:50 PM, David Blaikie <dblaikie at
gmail.com>
>>> wrote:
>>>
>>>>
>>>>
>>>> On Wed, Feb 10, 2016 at 3:55 PM, Alexey Samsonov via cfe-dev
<
>>>> cfe-dev at lists.llvm.org> wrote:
>>>>
>>>>> I mostly agree with what Richard and Justin said. Adding a
few notes
>>>>> about the general strategy we use:
>>>>>
>>>>> (1) lit tests which look "end-to-end" proved to
be way more convenient
>>>>> for testing runtime libraries than unit tests.
>>>>>
>>>> We do have
>>>>> the latter, and use them to provide test coverage for
utility
>>>>> functions, but we quite often accompany fix to the runtime
library with
>>>>> "end-to-end" small reproducer extracted from the
real-world code that
>>>>> exposed the issue.
>>>>> Incidentally, this tests a whole lot of other
functionality: Clang
>>>>> driver, frontend, LLVM passes, etc, but it's not the
intent of the test.
>>>>>
>>>>
>>>> Indeed - this is analogous to the tests for, say, LLD that use
llvm-mc
>>>> to produce the inputs rather than checking in object files.
That area is
>>>> open to some discussion as to just how many tools we should
rope in/how
>>>> isolated we should make tests (eg: maybe building the json
object file
>>>> format was going too far towards isolation? Not clear -
opinions differ).
>>>> But the point of the test is to test the compiler-rt
functionality that was
>>>> added/removed/modified.
>>>>
>>>> I think most people are in agreement with that, while
acknowledging the
>>>> fuzzy line about how isolated we might be.
>>>>
>>>
>>> Yes.
>>>
>>>
>>>>
>>>>
>>>>> These tests are sometimes platform-specific and poorly
portable, but
>>>>> they are more reliable (we make the same steps as the
>>>>> user of the compiler), and serve the purpose of
documentation.
>>>>>
>>>>> (2) If we change LLVM instrumentation - we add a test to
LLVM. If we
>>>>> change Clang code generation or driver behavior - we add
>>>>> a test to Clang. No excuses here.
>>>>>
>>>>> (3) Sometimes we still add a compiler-rt test for the
change in LLVM
>>>>> or Clang: e.g. if we enhance Clang frontend to teach UBSan
>>>>> to detecting yet another kind of overflow, it makes sense
to add a
>>>>> test to UBSan test-suite that demonstrates it, in addition
to
>>>>> Clang test verifying that we emit a call to UBSan runtime.
Also,
>>>>> compiler-rt test would allow us to verify that the actual
error report
>>>>> we present to the user is sane.
>>>>>
>>>>
>>>> This bit ^ is a bit unclear to me. If there was no change to
the UBSan
>>>> runtime, and the code generated by Clang is equivalent/similar
to an
>>>> existing use of the UBSan runtime - what is it that the new
compiler-rt
>>>> test is providing? (perhaps you could give a concrete example
you had in
>>>> mind to look at?)
>>>>
>>>
>>> See r235568 (change to Clang) followed by r235569 (change to
compiler-rt
>>> test). Now, it's a cheat because I'm fixing test, not
adding it. However, I
>>> would have definitely added it, if it was missing.
>>>
>>
>> Right, I think the difference here is "if it was missing" -
the test case
>> itself seems like it could be a reasonable one (are there other tests
of
>> the same compiler-rt functionality? (I assume the compiler-rt
functionality
>> is the implementation of sadd/ssub?))
>>
>>
>>> In this case, a change to Clang
>>> instrumentation (arguments passed to UBSan runtime callbacks)
improved
>>> the user-facing part of the tool, and compiler-rt test suite is a
good
>>> place to verify that.
>>>
>>
>> This seems like the problematic part - changes to LLVM improve the
>> user-facing part of Clang, but we don't add end-to-end tests of
that, as a
>> general rule. I'm trying to understand why the difference between
that and
>> compiler-rt
>>
>
> In what way do changes in LLVM change the user-facing part of Clang?
> It obviously depends on how broadly one defines user-facing. Is a 1%
> performance improvement from a particular optimization user-facing? Is
> better debug info accuracy user-facing? I'm not sure. But it seems
clear
> that "the user sees a diagnostic or not" definitely is.
>
There's more than just performance in LLVM - ABI features, and yes, I'd
argue some pieces of debug info are pretty user facing (as are some
optimizations). We also have the remarks system in place now. (also the
compiler crashing (or not) is pretty user facing).

> Also, I think part of this is that in compiler-rt there are usually more
> moving parts we don't control. E.g. it isn't just the interface
between
> LLVM and clang. The information needs to pass through archivers, linkers,
> runtime loaders, etc. that all may have issues that affect whether the user
> sees the final result. In general the interface between LLVM and clang has
> no middlemen so there really isn't anything to check.
>
Correctness/behavior of the compiler depends on those things too (linkers,
loaders, etc) to produce the final working product the user requested. If
we emitted symbols with the wrong linkage we could produce linker errors,
drop important entities, etc. But we don't generally test that the output
of LLVM/Clang produces the right binary when linked, we test that it
produces the right linkages on the resulting entities.

- David

>
> -- Sean Silva
>
>
>>
>>
>>>
>>>
>>
>>> You may argue that Clang test would have been enough (I disagree
with
>>> that), or that it qualifies as "adding coverage" (maybe).
>>>
>>>
>>>>
>>>>
>>>>> (4) True, we're intimidated by test-suite :) I feel
that current use
>>>>> of compiler-rt test suite to check compiler-rt libs better
follows
>>>>> the doctrine described by David.
>>>>>
>>>>
>>>> Which David? ;) (I guess David Li, not me)
>>>>
>>>
>>> Nope, paragraph 2 from your original email.
>>>
>>>
>>>> I think maybe what could be worth doing would be separating out
the
>>>> broader/intentionally "end to end" sort of tests from
the ones intended to
>>>> test compiler-rt in relative isolation.
>>>>
>>>
>>> It's really hard to draw the line here, even some of
compiler-rt unit
>>> tests require instrumentation, therefore depend on new features of
>>> Clang/LLVM. Unlike builtins, which are
>>> trivial to test in isolation, testing sanitizer runtimes in
isolation
>>> (w/o compiler) is often hard to implement (we tried to do so for
TSan, but
>>> found unit tests extremely hard to write),
>>> and is barely useful - compiler-rt runtimes don't consist of
modules
>>> (like LLVMCodeGen and LLVMMC for instance), and are never used w/o
the
>>> compiler anyway.
>>>
>>>
>>>>
>>>> Most importantly, I'd expect only the latter to run in a
"make
>>>> check-all" run, as we do for Clang/LLVM, etc.
>>>>
>>>
>>> And now we're getting to the goals :) Why would such a change
be good?
>>> Do you worry about the time it takes to execute the test suite?
>>>
>>>
>>>>
>>>>
>>>>> Also, there's significant complexity in compiler-rt
test suite that
>>>>> narrows the tests executed
>>>>> to those supported by current host.
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>
>>>>> On Wed, Feb 10, 2016 at 2:33 PM, Xinliang David Li via
cfe-dev <
>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On Wed, Feb 10, 2016 at 2:11 PM, Justin Bogner via
llvm-dev <
>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>
>>>>>>> David Blaikie via cfe-dev <cfe-dev at
lists.llvm.org> writes:
>>>>>>> > Recently had a bit of a digression in a review
thread related to
>>>>>>> some tests
>>>>>>> > going in to compiler-rt (
>>>>>>> >
>>>>>>>
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160208/330759.html
>>>>>>> > ) and there seems to be some disconnect at
least between my
>>>>>>> expectations
>>>>>>> > and reality. So I figured I'd have a bit
of a discussion out here
>>>>>>> on the
>>>>>>> > dev lists where there's a bit more
visibility.
>>>>>>> >
>>>>>>> > My basic expectation is that the lit tests in
any LLVM project
>>>>>>> except the
>>>>>>> > test-suite are targeted tests intended to test
only the
>>>>>>> functionality in
>>>>>>> > the project. This seems like a pretty well
accepted doctrine
>>>>>>> across most
>>>>>>> > LLVM projects - most visibly in Clang, where
we make a concerted
>>>>>>> effort not
>>>>>>> > to have tests that execute LLVM optimizations,
etc.
>>>>>>> >
>>>>>>> > There are exceptions/middle ground to this -
DIBuilder is in LLVM,
>>>>>>> but
>>>>>>> > essentially tested in Clang rather than
writing LLVM unit tests.
>>>>>>> It's
>>>>>>> > somewhat unavoidable that any of the IR
building code (IRBuilder,
>>>>>>> > DIBuilder, IR asm printing, etc) is
'tested' incidentally in Clang
>>>>>>> in
>>>>>>> > process of testing Clang's IR generation.
But these are seen as
>>>>>>> incidental,
>>>>>>> > not intentionally trying to cover LLVM with
Clang tests (we don't
>>>>>>> add a
>>>>>>> > Clang test if we add a new feature to
IRBuilder just to test the
>>>>>>> IRBuilder).
>>>>>>> >
>>>>>>> > Another case with some middle ground are
things like linker tests
>>>>>>> and
>>>>>>> > objdump, dwarfdump, etc - in theory to isolate
the test we would
>>>>>>> checkin
>>>>>>> > binaries (or the textual object representation
lld had for a
>>>>>>> while, etc) to
>>>>>>> > test those tools. Some tests instead checkin
assembly and assemble
>>>>>>> it with
>>>>>>> > llvm-mc. Again, not to cover llvm-mc, but on
the assumption that
>>>>>>> llvm-mc is
>>>>>>> > tested, and just using it as a tool to make
tests easier to
>>>>>>> maintain.
>>>>>>> >
>>>>>>> > So I was surprised to find that the
compiler-rt lit tests seem to
>>>>>>> diverge
>>>>>>> > from this philosophy & contain more
intentional end-to-end tests
>>>>>>> (eg:
>>>>>>> > adding a test there when making a fix to Clang
to add a counter to
>>>>>>> a
>>>>>>> > function that was otherwise missing a counter
- I'd expect that to
>>>>>>> be
>>>>>>> > tested in Clang and that there would already
be coverage in
>>>>>>> compiler-rt for
>>>>>>> > "if a function has a counter, does
compiler-rt do the right thing
>>>>>>> with that
>>>>>>> > counter" (testing whatever code in
compiler-rt needs to be
>>>>>>> tested)).
>>>>>>> >
>>>>>>> > Am I off base here? Are compiler-rt's
tests fundamentally
>>>>>>> different to the
>>>>>>> > rest of the LLVM project? Why? Should they
continue to be?
>>>>>>>
>>>>>>> I think there's a bit of grey area in terms
testing the runtime -
>>>>>>> generally it's pretty hard to use the runtime
without a fairly
>>>>>>> end-to-end test, so tests of the runtime often end
up looking pretty
>>>>>>> close to an end-to-end test.
>>>>>>>
>>>>>>> That said, I don't think that should be used as
an excuse to sneak
>>>>>>> arbitrary end-to-end tests into compiler-rt. We
should absolutely
>>>>>>> write
>>>>>>> tests in clang and llvm that we're inputting
what we expect to the
>>>>>>> runtime and try to keep the tests in compiler-rt as
focused on just
>>>>>>> exercising the runtime code as possible.
>>>>>>>
>>>>>>
>>>>>> Yes, we should not use compiler-rt tests as an excuse
of not adding
>>>>>> clang/LLVM test. The latter should always be added if
possible -- they are
>>>>>> platform independent and is the first level of defense.
runtime test's
>>>>>> focus is also more on the runtime lib itself and
interaction between
>>>>>>  runtime, compiler, binutils and other tools.
>>>>>>
>>>>>> David
>>>>>>
>>>>>>>
>>>>>>> IIUC, the correct place for integration tests in
general is somewhere
>>>>>>> like test-suite, but I think it's a bit
intimidating to some people
>>>>>>> to
>>>>>>> add new tests there (Are there docs on this?). I
suspect some of the
>>>>>>> profiling related tests in compiler-rt are doing a
bit much and
>>>>>>> should
>>>>>>> graduate to a spot in the test-suite (but I
don't have time to
>>>>>>> volunteer
>>>>>>> to do the work, unfortunately).
>>>>>>> _______________________________________________
>>>>>>> LLVM Developers mailing list
>>>>>>> llvm-dev at lists.llvm.org
>>>>>>>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> cfe-dev mailing list
>>>>>> cfe-dev at lists.llvm.org
>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Alexey Samsonov
>>>>> vonosmas at gmail.com
>>>>>
>>>>> _______________________________________________
>>>>> cfe-dev mailing list
>>>>> cfe-dev at lists.llvm.org
>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>
>>>>>
>>>>
>>>
>>>
>>> --
>>> Alexey Samsonov
>>> vonosmas at gmail.com
>>>
>>
>>
>> _______________________________________________
>> cfe-dev mailing list
>> cfe-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>
>>
>
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On Fri, Feb 26, 2016 at 1:11 PM, David Blaikie <dblaikie at gmail.com>
wrote:
>
>
> On Fri, Feb 26, 2016 at 1:07 PM, Sean Silva <chisophugis at
gmail.com> wrote:
>
>>
>>
>> On Wed, Feb 17, 2016 at 8:45 AM, David Blaikie via cfe-dev <
>> cfe-dev at lists.llvm.org> wrote:
>>
>>>
>>>
>>> On Fri, Feb 12, 2016 at 5:43 PM, Alexey Samsonov <vonosmas at
gmail.com>
>>> wrote:
>>>
>>>>
>>>>
>>>> On Thu, Feb 11, 2016 at 1:50 PM, David Blaikie <dblaikie at
gmail.com>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> On Wed, Feb 10, 2016 at 3:55 PM, Alexey Samsonov via
cfe-dev <
>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>
>>>>>> I mostly agree with what Richard and Justin said.
Adding a few notes
>>>>>> about the general strategy we use:
>>>>>>
>>>>>> (1) lit tests which look "end-to-end" proved
to be way more
>>>>>> convenient for testing runtime libraries than unit
tests.
>>>>>>
>>>>> We do have
>>>>>> the latter, and use them to provide test coverage for
utility
>>>>>> functions, but we quite often accompany fix to the
runtime library with
>>>>>> "end-to-end" small reproducer extracted from
the real-world code that
>>>>>> exposed the issue.
>>>>>> Incidentally, this tests a whole lot of other
functionality: Clang
>>>>>> driver, frontend, LLVM passes, etc, but it's not
the intent of the test.
>>>>>>
>>>>>
>>>>> Indeed - this is analogous to the tests for, say, LLD that
use llvm-mc
>>>>> to produce the inputs rather than checking in object files.
That area is
>>>>> open to some discussion as to just how many tools we should
rope in/how
>>>>> isolated we should make tests (eg: maybe building the json
object file
>>>>> format was going too far towards isolation? Not clear -
opinions differ).
>>>>> But the point of the test is to test the compiler-rt
functionality that was
>>>>> added/removed/modified.
>>>>>
>>>>> I think most people are in agreement with that, while
acknowledging
>>>>> the fuzzy line about how isolated we might be.
>>>>>
>>>>
>>>> Yes.
>>>>
>>>>
>>>>>
>>>>>
>>>>>> These tests are sometimes platform-specific and poorly
portable, but
>>>>>> they are more reliable (we make the same steps as the
>>>>>> user of the compiler), and serve the purpose of
documentation.
>>>>>>
>>>>>> (2) If we change LLVM instrumentation - we add a test
to LLVM. If we
>>>>>> change Clang code generation or driver behavior - we
add
>>>>>> a test to Clang. No excuses here.
>>>>>>
>>>>>> (3) Sometimes we still add a compiler-rt test for the
change in LLVM
>>>>>> or Clang: e.g. if we enhance Clang frontend to teach
UBSan
>>>>>> to detecting yet another kind of overflow, it makes
sense to add a
>>>>>> test to UBSan test-suite that demonstrates it, in
addition to
>>>>>> Clang test verifying that we emit a call to UBSan
runtime. Also,
>>>>>> compiler-rt test would allow us to verify that the
actual error report
>>>>>> we present to the user is sane.
>>>>>>
>>>>>
>>>>> This bit ^ is a bit unclear to me. If there was no change
to the UBSan
>>>>> runtime, and the code generated by Clang is
equivalent/similar to an
>>>>> existing use of the UBSan runtime - what is it that the new
compiler-rt
>>>>> test is providing? (perhaps you could give a concrete
example you had in
>>>>> mind to look at?)
>>>>>
>>>>
>>>> See r235568 (change to Clang) followed by r235569 (change to
>>>> compiler-rt test). Now, it's a cheat because I'm fixing
test, not adding
>>>> it. However, I would have definitely added it, if it was
missing.
>>>>
>>>
>>> Right, I think the difference here is "if it was missing"
- the test
>>> case itself seems like it could be a reasonable one (are there
other tests
>>> of the same compiler-rt functionality? (I assume the compiler-rt
>>> functionality is the implementation of sadd/ssub?))
>>>
>>>
>>>> In this case, a change to Clang
>>>> instrumentation (arguments passed to UBSan runtime callbacks)
improved
>>>> the user-facing part of the tool, and compiler-rt test suite is
a good
>>>> place to verify that.
>>>>
>>>
>>> This seems like the problematic part - changes to LLVM improve the
>>> user-facing part of Clang, but we don't add end-to-end tests of
that, as a
>>> general rule. I'm trying to understand why the difference
between that and
>>> compiler-rt
>>>
>>
>> In what way do changes in LLVM change the user-facing part of Clang?
>> It obviously depends on how broadly one defines user-facing. Is a 1%
>> performance improvement from a particular optimization user-facing? Is
>> better debug info accuracy user-facing? I'm not sure. But it seems
clear
>> that "the user sees a diagnostic or not" definitely is.
>>
>
> There's more than just performance in LLVM - ABI features, and yes,
I'd
> argue some pieces of debug info are pretty user facing (as are some
> optimizations). We also have the remarks system in place now. (also the
> compiler crashing (or not) is pretty user facing).
>
>
>> Also, I think part of this is that in compiler-rt there are usually
more
>> moving parts we don't control. E.g. it isn't just the interface
between
>> LLVM and clang. The information needs to pass through archivers,
linkers,
>> runtime loaders, etc. that all may have issues that affect whether the
user
>> sees the final result. In general the interface between LLVM and clang
has
>> no middlemen so there really isn't anything to check.
>>
>
> Correctness/behavior of the compiler depends on those things too (linkers,
> loaders, etc) to produce the final working product the user requested. If
> we emitted symbols with the wrong linkage we could produce linker errors,
> drop important entities, etc. But we don't generally test that the
output
> of LLVM/Clang produces the right binary when linked, we test that it
> produces the right linkages on the resulting entities.
>
Sure, but verifying the Clang compiles/links a certain source file
successfully can easily live in a dedicated test-suite, even after it's
moved to GitHub, because probably it would be compiler-agnostic, and
wouldn't change frequently.

That said, I wouldn't mind having more Clang end-to-end tests, but the
major issue with actually invoking linkers and using system libraries is
portability.
These portability requirements are a lesser issue for sanitizers, because
we support only a handful of platforms.


> - David
>
>
>>
>> -- Sean Silva
>>
>>
>>>
>>>
>>>>
>>>>
>>>
>>>> You may argue that Clang test would have been enough (I
disagree with
>>>> that), or that it qualifies as "adding coverage"
(maybe).
>>>>
>>>>
>>>>>
>>>>>
>>>>>> (4) True, we're intimidated by test-suite :) I feel
that current use
>>>>>> of compiler-rt test suite to check compiler-rt libs
better follows
>>>>>> the doctrine described by David.
>>>>>>
>>>>>
>>>>> Which David? ;) (I guess David Li, not me)
>>>>>
>>>>
>>>> Nope, paragraph 2 from your original email.
>>>>
>>>>
>>>>> I think maybe what could be worth doing would be separating
out the
>>>>> broader/intentionally "end to end" sort of tests
from the ones intended to
>>>>> test compiler-rt in relative isolation.
>>>>>
>>>>
>>>> It's really hard to draw the line here, even some of
compiler-rt unit
>>>> tests require instrumentation, therefore depend on new features
of
>>>> Clang/LLVM. Unlike builtins, which are
>>>> trivial to test in isolation, testing sanitizer runtimes in
isolation
>>>> (w/o compiler) is often hard to implement (we tried to do so
for TSan, but
>>>> found unit tests extremely hard to write),
>>>> and is barely useful - compiler-rt runtimes don't consist
of modules
>>>> (like LLVMCodeGen and LLVMMC for instance), and are never used
w/o the
>>>> compiler anyway.
>>>>
>>>>
>>>>>
>>>>> Most importantly, I'd expect only the latter to run in
a "make
>>>>> check-all" run, as we do for Clang/LLVM, etc.
>>>>>
>>>>
>>>> And now we're getting to the goals :) Why would such a
change be good?
>>>> Do you worry about the time it takes to execute the test suite?
>>>>
>>>>
>>>>>
>>>>>
>>>>>> Also, there's significant complexity in compiler-rt
test suite that
>>>>>> narrows the tests executed
>>>>>> to those supported by current host.
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> On Wed, Feb 10, 2016 at 2:33 PM, Xinliang David Li via
cfe-dev <
>>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Wed, Feb 10, 2016 at 2:11 PM, Justin Bogner via
llvm-dev <
>>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>>
>>>>>>>> David Blaikie via cfe-dev <cfe-dev at
lists.llvm.org> writes:
>>>>>>>> > Recently had a bit of a digression in a
review thread related to
>>>>>>>> some tests
>>>>>>>> > going in to compiler-rt (
>>>>>>>> >
>>>>>>>>
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160208/330759.html
>>>>>>>> > ) and there seems to be some disconnect at
least between my
>>>>>>>> expectations
>>>>>>>> > and reality. So I figured I'd have a
bit of a discussion out here
>>>>>>>> on the
>>>>>>>> > dev lists where there's a bit more
visibility.
>>>>>>>> >
>>>>>>>> > My basic expectation is that the lit tests
in any LLVM project
>>>>>>>> except the
>>>>>>>> > test-suite are targeted tests intended to
test only the
>>>>>>>> functionality in
>>>>>>>> > the project. This seems like a pretty well
accepted doctrine
>>>>>>>> across most
>>>>>>>> > LLVM projects - most visibly in Clang,
where we make a concerted
>>>>>>>> effort not
>>>>>>>> > to have tests that execute LLVM
optimizations, etc.
>>>>>>>> >
>>>>>>>> > There are exceptions/middle ground to this
- DIBuilder is in
>>>>>>>> LLVM, but
>>>>>>>> > essentially tested in Clang rather than
writing LLVM unit tests.
>>>>>>>> It's
>>>>>>>> > somewhat unavoidable that any of the IR
building code (IRBuilder,
>>>>>>>> > DIBuilder, IR asm printing, etc) is
'tested' incidentally in
>>>>>>>> Clang in
>>>>>>>> > process of testing Clang's IR
generation. But these are seen as
>>>>>>>> incidental,
>>>>>>>> > not intentionally trying to cover LLVM
with Clang tests (we don't
>>>>>>>> add a
>>>>>>>> > Clang test if we add a new feature to
IRBuilder just to test the
>>>>>>>> IRBuilder).
>>>>>>>> >
>>>>>>>> > Another case with some middle ground are
things like linker tests
>>>>>>>> and
>>>>>>>> > objdump, dwarfdump, etc - in theory to
isolate the test we would
>>>>>>>> checkin
>>>>>>>> > binaries (or the textual object
representation lld had for a
>>>>>>>> while, etc) to
>>>>>>>> > test those tools. Some tests instead
checkin assembly and
>>>>>>>> assemble it with
>>>>>>>> > llvm-mc. Again, not to cover llvm-mc, but
on the assumption that
>>>>>>>> llvm-mc is
>>>>>>>> > tested, and just using it as a tool to
make tests easier to
>>>>>>>> maintain.
>>>>>>>> >
>>>>>>>> > So I was surprised to find that the
compiler-rt lit tests seem to
>>>>>>>> diverge
>>>>>>>> > from this philosophy & contain more
intentional end-to-end tests
>>>>>>>> (eg:
>>>>>>>> > adding a test there when making a fix to
Clang to add a counter
>>>>>>>> to a
>>>>>>>> > function that was otherwise missing a
counter - I'd expect that
>>>>>>>> to be
>>>>>>>> > tested in Clang and that there would
already be coverage in
>>>>>>>> compiler-rt for
>>>>>>>> > "if a function has a counter, does
compiler-rt do the right thing
>>>>>>>> with that
>>>>>>>> > counter" (testing whatever code in
compiler-rt needs to be
>>>>>>>> tested)).
>>>>>>>> >
>>>>>>>> > Am I off base here? Are compiler-rt's
tests fundamentally
>>>>>>>> different to the
>>>>>>>> > rest of the LLVM project? Why? Should they
continue to be?
>>>>>>>>
>>>>>>>> I think there's a bit of grey area in terms
testing the runtime -
>>>>>>>> generally it's pretty hard to use the
runtime without a fairly
>>>>>>>> end-to-end test, so tests of the runtime often
end up looking pretty
>>>>>>>> close to an end-to-end test.
>>>>>>>>
>>>>>>>> That said, I don't think that should be
used as an excuse to sneak
>>>>>>>> arbitrary end-to-end tests into compiler-rt. We
should absolutely
>>>>>>>> write
>>>>>>>> tests in clang and llvm that we're
inputting what we expect to the
>>>>>>>> runtime and try to keep the tests in
compiler-rt as focused on just
>>>>>>>> exercising the runtime code as possible.
>>>>>>>>
>>>>>>>
>>>>>>> Yes, we should not use compiler-rt tests as an
excuse of not adding
>>>>>>> clang/LLVM test. The latter should always be added
if possible -- they are
>>>>>>> platform independent and is the first level of
defense.  runtime test's
>>>>>>> focus is also more on the runtime lib itself and
interaction between
>>>>>>>  runtime, compiler, binutils and other tools.
>>>>>>>
>>>>>>> David
>>>>>>>
>>>>>>>>
>>>>>>>> IIUC, the correct place for integration tests
in general is
>>>>>>>> somewhere
>>>>>>>> like test-suite, but I think it's a bit
intimidating to some people
>>>>>>>> to
>>>>>>>> add new tests there (Are there docs on this?).
I suspect some of the
>>>>>>>> profiling related tests in compiler-rt are
doing a bit much and
>>>>>>>> should
>>>>>>>> graduate to a spot in the test-suite (but I
don't have time to
>>>>>>>> volunteer
>>>>>>>> to do the work, unfortunately).
>>>>>>>> _______________________________________________
>>>>>>>> LLVM Developers mailing list
>>>>>>>> llvm-dev at lists.llvm.org
>>>>>>>>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> cfe-dev mailing list
>>>>>>> cfe-dev at lists.llvm.org
>>>>>>>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Alexey Samsonov
>>>>>> vonosmas at gmail.com
>>>>>>
>>>>>> _______________________________________________
>>>>>> cfe-dev mailing list
>>>>>> cfe-dev at lists.llvm.org
>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Alexey Samsonov
>>>> vonosmas at gmail.com
>>>>
>>>
>>>
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>
>>>
>>
>

-- 
Alexey Samsonov
vonosmas at gmail.com
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On Fri, Feb 26, 2016 at 1:11 PM, David Blaikie <dblaikie at gmail.com>
wrote:
>
>
> On Fri, Feb 26, 2016 at 1:07 PM, Sean Silva <chisophugis at
gmail.com> wrote:
>
>>
>>
>> On Wed, Feb 17, 2016 at 8:45 AM, David Blaikie via cfe-dev <
>> cfe-dev at lists.llvm.org> wrote:
>>
>>>
>>>
>>> On Fri, Feb 12, 2016 at 5:43 PM, Alexey Samsonov <vonosmas at
gmail.com>
>>> wrote:
>>>
>>>>
>>>>
>>>> On Thu, Feb 11, 2016 at 1:50 PM, David Blaikie <dblaikie at
gmail.com>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> On Wed, Feb 10, 2016 at 3:55 PM, Alexey Samsonov via
cfe-dev <
>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>
>>>>>> I mostly agree with what Richard and Justin said.
Adding a few notes
>>>>>> about the general strategy we use:
>>>>>>
>>>>>> (1) lit tests which look "end-to-end" proved
to be way more
>>>>>> convenient for testing runtime libraries than unit
tests.
>>>>>>
>>>>> We do have
>>>>>> the latter, and use them to provide test coverage for
utility
>>>>>> functions, but we quite often accompany fix to the
runtime library with
>>>>>> "end-to-end" small reproducer extracted from
the real-world code that
>>>>>> exposed the issue.
>>>>>> Incidentally, this tests a whole lot of other
functionality: Clang
>>>>>> driver, frontend, LLVM passes, etc, but it's not
the intent of the test.
>>>>>>
>>>>>
>>>>> Indeed - this is analogous to the tests for, say, LLD that
use llvm-mc
>>>>> to produce the inputs rather than checking in object files.
That area is
>>>>> open to some discussion as to just how many tools we should
rope in/how
>>>>> isolated we should make tests (eg: maybe building the json
object file
>>>>> format was going too far towards isolation? Not clear -
opinions differ).
>>>>> But the point of the test is to test the compiler-rt
functionality that was
>>>>> added/removed/modified.
>>>>>
>>>>> I think most people are in agreement with that, while
acknowledging
>>>>> the fuzzy line about how isolated we might be.
>>>>>
>>>>
>>>> Yes.
>>>>
>>>>
>>>>>
>>>>>
>>>>>> These tests are sometimes platform-specific and poorly
portable, but
>>>>>> they are more reliable (we make the same steps as the
>>>>>> user of the compiler), and serve the purpose of
documentation.
>>>>>>
>>>>>> (2) If we change LLVM instrumentation - we add a test
to LLVM. If we
>>>>>> change Clang code generation or driver behavior - we
add
>>>>>> a test to Clang. No excuses here.
>>>>>>
>>>>>> (3) Sometimes we still add a compiler-rt test for the
change in LLVM
>>>>>> or Clang: e.g. if we enhance Clang frontend to teach
UBSan
>>>>>> to detecting yet another kind of overflow, it makes
sense to add a
>>>>>> test to UBSan test-suite that demonstrates it, in
addition to
>>>>>> Clang test verifying that we emit a call to UBSan
runtime. Also,
>>>>>> compiler-rt test would allow us to verify that the
actual error report
>>>>>> we present to the user is sane.
>>>>>>
>>>>>
>>>>> This bit ^ is a bit unclear to me. If there was no change
to the UBSan
>>>>> runtime, and the code generated by Clang is
equivalent/similar to an
>>>>> existing use of the UBSan runtime - what is it that the new
compiler-rt
>>>>> test is providing? (perhaps you could give a concrete
example you had in
>>>>> mind to look at?)
>>>>>
>>>>
>>>> See r235568 (change to Clang) followed by r235569 (change to
>>>> compiler-rt test). Now, it's a cheat because I'm fixing
test, not adding
>>>> it. However, I would have definitely added it, if it was
missing.
>>>>
>>>
>>> Right, I think the difference here is "if it was missing"
- the test
>>> case itself seems like it could be a reasonable one (are there
other tests
>>> of the same compiler-rt functionality? (I assume the compiler-rt
>>> functionality is the implementation of sadd/ssub?))
>>>
>>>
>>>> In this case, a change to Clang
>>>> instrumentation (arguments passed to UBSan runtime callbacks)
improved
>>>> the user-facing part of the tool, and compiler-rt test suite is
a good
>>>> place to verify that.
>>>>
>>>
>>> This seems like the problematic part - changes to LLVM improve the
>>> user-facing part of Clang, but we don't add end-to-end tests of
that, as a
>>> general rule. I'm trying to understand why the difference
between that and
>>> compiler-rt
>>>
>>
>> In what way do changes in LLVM change the user-facing part of Clang?
>> It obviously depends on how broadly one defines user-facing. Is a 1%
>> performance improvement from a particular optimization user-facing? Is
>> better debug info accuracy user-facing? I'm not sure. But it seems
clear
>> that "the user sees a diagnostic or not" definitely is.
>>
>
> There's more than just performance in LLVM - ABI features, and yes,
I'd
> argue some pieces of debug info are pretty user facing (as are some
> optimizations). We also have the remarks system in place now. (also the
> compiler crashing (or not) is pretty user facing).
>
I'd argue that we probably should have some sort of integration tests for
ABI features. I think at the moment we're getting by thanks to self-hosting
and regularly building lots of real-world programs with ToT-ish compilers.

-- Sean Silva

>
>
>> Also, I think part of this is that in compiler-rt there are usually
more
>> moving parts we don't control. E.g. it isn't just the interface
between
>> LLVM and clang. The information needs to pass through archivers,
linkers,
>> runtime loaders, etc. that all may have issues that affect whether the
user
>> sees the final result. In general the interface between LLVM and clang
has
>> no middlemen so there really isn't anything to check.
>>
>
> Correctness/behavior of the compiler depends on those things too (linkers,
> loaders, etc) to produce the final working product the user requested. If
> we emitted symbols with the wrong linkage we could produce linker errors,
> drop important entities, etc. But we don't generally test that the
output
> of LLVM/Clang produces the right binary when linked, we test that it
> produces the right linkages on the resulting entities.
>
> - David
>
>
>>
>> -- Sean Silva
>>
>>
>>>
>>>
>>>>
>>>>
>>>
>>>> You may argue that Clang test would have been enough (I
disagree with
>>>> that), or that it qualifies as "adding coverage"
(maybe).
>>>>
>>>>
>>>>>
>>>>>
>>>>>> (4) True, we're intimidated by test-suite :) I feel
that current use
>>>>>> of compiler-rt test suite to check compiler-rt libs
better follows
>>>>>> the doctrine described by David.
>>>>>>
>>>>>
>>>>> Which David? ;) (I guess David Li, not me)
>>>>>
>>>>
>>>> Nope, paragraph 2 from your original email.
>>>>
>>>>
>>>>> I think maybe what could be worth doing would be separating
out the
>>>>> broader/intentionally "end to end" sort of tests
from the ones intended to
>>>>> test compiler-rt in relative isolation.
>>>>>
>>>>
>>>> It's really hard to draw the line here, even some of
compiler-rt unit
>>>> tests require instrumentation, therefore depend on new features
of
>>>> Clang/LLVM. Unlike builtins, which are
>>>> trivial to test in isolation, testing sanitizer runtimes in
isolation
>>>> (w/o compiler) is often hard to implement (we tried to do so
for TSan, but
>>>> found unit tests extremely hard to write),
>>>> and is barely useful - compiler-rt runtimes don't consist
of modules
>>>> (like LLVMCodeGen and LLVMMC for instance), and are never used
w/o the
>>>> compiler anyway.
>>>>
>>>>
>>>>>
>>>>> Most importantly, I'd expect only the latter to run in
a "make
>>>>> check-all" run, as we do for Clang/LLVM, etc.
>>>>>
>>>>
>>>> And now we're getting to the goals :) Why would such a
change be good?
>>>> Do you worry about the time it takes to execute the test suite?
>>>>
>>>>
>>>>>
>>>>>
>>>>>> Also, there's significant complexity in compiler-rt
test suite that
>>>>>> narrows the tests executed
>>>>>> to those supported by current host.
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>>
>>>>>> On Wed, Feb 10, 2016 at 2:33 PM, Xinliang David Li via
cfe-dev <
>>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Wed, Feb 10, 2016 at 2:11 PM, Justin Bogner via
llvm-dev <
>>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>>
>>>>>>>> David Blaikie via cfe-dev <cfe-dev at
lists.llvm.org> writes:
>>>>>>>> > Recently had a bit of a digression in a
review thread related to
>>>>>>>> some tests
>>>>>>>> > going in to compiler-rt (
>>>>>>>> >
>>>>>>>>
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160208/330759.html
>>>>>>>> > ) and there seems to be some disconnect at
least between my
>>>>>>>> expectations
>>>>>>>> > and reality. So I figured I'd have a
bit of a discussion out here
>>>>>>>> on the
>>>>>>>> > dev lists where there's a bit more
visibility.
>>>>>>>> >
>>>>>>>> > My basic expectation is that the lit tests
in any LLVM project
>>>>>>>> except the
>>>>>>>> > test-suite are targeted tests intended to
test only the
>>>>>>>> functionality in
>>>>>>>> > the project. This seems like a pretty well
accepted doctrine
>>>>>>>> across most
>>>>>>>> > LLVM projects - most visibly in Clang,
where we make a concerted
>>>>>>>> effort not
>>>>>>>> > to have tests that execute LLVM
optimizations, etc.
>>>>>>>> >
>>>>>>>> > There are exceptions/middle ground to this
- DIBuilder is in
>>>>>>>> LLVM, but
>>>>>>>> > essentially tested in Clang rather than
writing LLVM unit tests.
>>>>>>>> It's
>>>>>>>> > somewhat unavoidable that any of the IR
building code (IRBuilder,
>>>>>>>> > DIBuilder, IR asm printing, etc) is
'tested' incidentally in
>>>>>>>> Clang in
>>>>>>>> > process of testing Clang's IR
generation. But these are seen as
>>>>>>>> incidental,
>>>>>>>> > not intentionally trying to cover LLVM
with Clang tests (we don't
>>>>>>>> add a
>>>>>>>> > Clang test if we add a new feature to
IRBuilder just to test the
>>>>>>>> IRBuilder).
>>>>>>>> >
>>>>>>>> > Another case with some middle ground are
things like linker tests
>>>>>>>> and
>>>>>>>> > objdump, dwarfdump, etc - in theory to
isolate the test we would
>>>>>>>> checkin
>>>>>>>> > binaries (or the textual object
representation lld had for a
>>>>>>>> while, etc) to
>>>>>>>> > test those tools. Some tests instead
checkin assembly and
>>>>>>>> assemble it with
>>>>>>>> > llvm-mc. Again, not to cover llvm-mc, but
on the assumption that
>>>>>>>> llvm-mc is
>>>>>>>> > tested, and just using it as a tool to
make tests easier to
>>>>>>>> maintain.
>>>>>>>> >
>>>>>>>> > So I was surprised to find that the
compiler-rt lit tests seem to
>>>>>>>> diverge
>>>>>>>> > from this philosophy & contain more
intentional end-to-end tests
>>>>>>>> (eg:
>>>>>>>> > adding a test there when making a fix to
Clang to add a counter
>>>>>>>> to a
>>>>>>>> > function that was otherwise missing a
counter - I'd expect that
>>>>>>>> to be
>>>>>>>> > tested in Clang and that there would
already be coverage in
>>>>>>>> compiler-rt for
>>>>>>>> > "if a function has a counter, does
compiler-rt do the right thing
>>>>>>>> with that
>>>>>>>> > counter" (testing whatever code in
compiler-rt needs to be
>>>>>>>> tested)).
>>>>>>>> >
>>>>>>>> > Am I off base here? Are compiler-rt's
tests fundamentally
>>>>>>>> different to the
>>>>>>>> > rest of the LLVM project? Why? Should they
continue to be?
>>>>>>>>
>>>>>>>> I think there's a bit of grey area in terms
testing the runtime -
>>>>>>>> generally it's pretty hard to use the
runtime without a fairly
>>>>>>>> end-to-end test, so tests of the runtime often
end up looking pretty
>>>>>>>> close to an end-to-end test.
>>>>>>>>
>>>>>>>> That said, I don't think that should be
used as an excuse to sneak
>>>>>>>> arbitrary end-to-end tests into compiler-rt. We
should absolutely
>>>>>>>> write
>>>>>>>> tests in clang and llvm that we're
inputting what we expect to the
>>>>>>>> runtime and try to keep the tests in
compiler-rt as focused on just
>>>>>>>> exercising the runtime code as possible.
>>>>>>>>
>>>>>>>
>>>>>>> Yes, we should not use compiler-rt tests as an
excuse of not adding
>>>>>>> clang/LLVM test. The latter should always be added
if possible -- they are
>>>>>>> platform independent and is the first level of
defense.  runtime test's
>>>>>>> focus is also more on the runtime lib itself and
interaction between
>>>>>>>  runtime, compiler, binutils and other tools.
>>>>>>>
>>>>>>> David
>>>>>>>
>>>>>>>>
>>>>>>>> IIUC, the correct place for integration tests
in general is
>>>>>>>> somewhere
>>>>>>>> like test-suite, but I think it's a bit
intimidating to some people
>>>>>>>> to
>>>>>>>> add new tests there (Are there docs on this?).
I suspect some of the
>>>>>>>> profiling related tests in compiler-rt are
doing a bit much and
>>>>>>>> should
>>>>>>>> graduate to a spot in the test-suite (but I
don't have time to
>>>>>>>> volunteer
>>>>>>>> to do the work, unfortunately).
>>>>>>>> _______________________________________________
>>>>>>>> LLVM Developers mailing list
>>>>>>>> llvm-dev at lists.llvm.org
>>>>>>>>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> cfe-dev mailing list
>>>>>>> cfe-dev at lists.llvm.org
>>>>>>>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Alexey Samsonov
>>>>>> vonosmas at gmail.com
>>>>>>
>>>>>> _______________________________________________
>>>>>> cfe-dev mailing list
>>>>>> cfe-dev at lists.llvm.org
>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>> --
>>>> Alexey Samsonov
>>>> vonosmas at gmail.com
>>>>
>>>
>>>
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at lists.llvm.org
>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>
>>>
>>
>
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On Fri, Feb 26, 2016 at 1:31 PM, Sean Silva <chisophugis at gmail.com>
wrote:
>
>
> On Fri, Feb 26, 2016 at 1:11 PM, David Blaikie <dblaikie at
gmail.com> wrote:
>
>>
>>
>> On Fri, Feb 26, 2016 at 1:07 PM, Sean Silva <chisophugis at
gmail.com>
>> wrote:
>>
>>>
>>>
>>> On Wed, Feb 17, 2016 at 8:45 AM, David Blaikie via cfe-dev <
>>> cfe-dev at lists.llvm.org> wrote:
>>>
>>>>
>>>>
>>>> On Fri, Feb 12, 2016 at 5:43 PM, Alexey Samsonov <vonosmas
at gmail.com>
>>>> wrote:
>>>>
>>>>>
>>>>>
>>>>> On Thu, Feb 11, 2016 at 1:50 PM, David Blaikie <dblaikie
at gmail.com>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>>
>>>>>> On Wed, Feb 10, 2016 at 3:55 PM, Alexey Samsonov via
cfe-dev <
>>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>>
>>>>>>> I mostly agree with what Richard and Justin said.
Adding a few notes
>>>>>>> about the general strategy we use:
>>>>>>>
>>>>>>> (1) lit tests which look "end-to-end"
proved to be way more
>>>>>>> convenient for testing runtime libraries than unit
tests.
>>>>>>>
>>>>>> We do have
>>>>>>> the latter, and use them to provide test coverage
for utility
>>>>>>> functions, but we quite often accompany fix to the
runtime library with
>>>>>>> "end-to-end" small reproducer extracted
from the real-world code
>>>>>>> that exposed the issue.
>>>>>>> Incidentally, this tests a whole lot of other
functionality: Clang
>>>>>>> driver, frontend, LLVM passes, etc, but it's
not the intent of the test.
>>>>>>>
>>>>>>
>>>>>> Indeed - this is analogous to the tests for, say, LLD
that use
>>>>>> llvm-mc to produce the inputs rather than checking in
object files. That
>>>>>> area is open to some discussion as to just how many
tools we should rope
>>>>>> in/how isolated we should make tests (eg: maybe
building the json object
>>>>>> file format was going too far towards isolation? Not
clear - opinions
>>>>>> differ). But the point of the test is to test the
compiler-rt functionality
>>>>>> that was added/removed/modified.
>>>>>>
>>>>>> I think most people are in agreement with that, while
acknowledging
>>>>>> the fuzzy line about how isolated we might be.
>>>>>>
>>>>>
>>>>> Yes.
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>>> These tests are sometimes platform-specific and
poorly portable, but
>>>>>>> they are more reliable (we make the same steps as
the
>>>>>>> user of the compiler), and serve the purpose of
documentation.
>>>>>>>
>>>>>>> (2) If we change LLVM instrumentation - we add a
test to LLVM. If we
>>>>>>> change Clang code generation or driver behavior -
we add
>>>>>>> a test to Clang. No excuses here.
>>>>>>>
>>>>>>> (3) Sometimes we still add a compiler-rt test for
the change in LLVM
>>>>>>> or Clang: e.g. if we enhance Clang frontend to
teach UBSan
>>>>>>> to detecting yet another kind of overflow, it makes
sense to add a
>>>>>>> test to UBSan test-suite that demonstrates it, in
addition to
>>>>>>> Clang test verifying that we emit a call to UBSan
runtime. Also,
>>>>>>> compiler-rt test would allow us to verify that the
actual error report
>>>>>>> we present to the user is sane.
>>>>>>>
>>>>>>
>>>>>> This bit ^ is a bit unclear to me. If there was no
change to the
>>>>>> UBSan runtime, and the code generated by Clang is
equivalent/similar to an
>>>>>> existing use of the UBSan runtime - what is it that the
new compiler-rt
>>>>>> test is providing? (perhaps you could give a concrete
example you had in
>>>>>> mind to look at?)
>>>>>>
>>>>>
>>>>> See r235568 (change to Clang) followed by r235569 (change
to
>>>>> compiler-rt test). Now, it's a cheat because I'm
fixing test, not adding
>>>>> it. However, I would have definitely added it, if it was
missing.
>>>>>
>>>>
>>>> Right, I think the difference here is "if it was
missing" - the test
>>>> case itself seems like it could be a reasonable one (are there
other tests
>>>> of the same compiler-rt functionality? (I assume the
compiler-rt
>>>> functionality is the implementation of sadd/ssub?))
>>>>
>>>>
>>>>> In this case, a change to Clang
>>>>> instrumentation (arguments passed to UBSan runtime
callbacks) improved
>>>>> the user-facing part of the tool, and compiler-rt test
suite is a good
>>>>> place to verify that.
>>>>>
>>>>
>>>> This seems like the problematic part - changes to LLVM improve
the
>>>> user-facing part of Clang, but we don't add end-to-end
tests of that, as a
>>>> general rule. I'm trying to understand why the difference
between that and
>>>> compiler-rt
>>>>
>>>
>>> In what way do changes in LLVM change the user-facing part of
Clang?
>>> It obviously depends on how broadly one defines user-facing. Is a
1%
>>> performance improvement from a particular optimization user-facing?
Is
>>> better debug info accuracy user-facing? I'm not sure. But it
seems clear
>>> that "the user sees a diagnostic or not" definitely is.
>>>
>>
>> There's more than just performance in LLVM - ABI features, and yes,
I'd
>> argue some pieces of debug info are pretty user facing (as are some
>> optimizations). We also have the remarks system in place now. (also the
>> compiler crashing (or not) is pretty user facing).
>>
>
> I'd argue that we probably should have some sort of integration tests
for
> ABI features. I think at the moment we're getting by thanks to
self-hosting
> and regularly building lots of real-world programs with ToT-ish compilers.
>
Perhaps so, but I'd argue that they shouldn't be run as part of
"make
check" & should be in a separate test grouping (probably mostly run by
buildbots) for the purpose of integration testing. We've made a pretty
conscious, deliberate, and consistent effort to not do integration testing
across the LLVM projects in "make check"-like testing, and to fix it
where
we do find it. It seems to me that compiler-rt diverged from that approach
and I'm not really in favor of that divergence.

- David

>
> -- Sean Silva
>
>
>>
>>
>>> Also, I think part of this is that in compiler-rt there are usually
more
>>> moving parts we don't control. E.g. it isn't just the
interface between
>>> LLVM and clang. The information needs to pass through archivers,
linkers,
>>> runtime loaders, etc. that all may have issues that affect whether
the user
>>> sees the final result. In general the interface between LLVM and
clang has
>>> no middlemen so there really isn't anything to check.
>>>
>>
>> Correctness/behavior of the compiler depends on those things too
>> (linkers, loaders, etc) to produce the final working product the user
>> requested. If we emitted symbols with the wrong linkage we could
produce
>> linker errors, drop important entities, etc. But we don't generally
test
>> that the output of LLVM/Clang produces the right binary when linked, we
>> test that it produces the right linkages on the resulting entities.
>>
>> - David
>>
>>
>>>
>>> -- Sean Silva
>>>
>>>
>>>>
>>>>
>>>>>
>>>>>
>>>>
>>>>> You may argue that Clang test would have been enough (I
disagree with
>>>>> that), or that it qualifies as "adding coverage"
(maybe).
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>>> (4) True, we're intimidated by test-suite :) I
feel that current use
>>>>>>> of compiler-rt test suite to check compiler-rt libs
better follows
>>>>>>> the doctrine described by David.
>>>>>>>
>>>>>>
>>>>>> Which David? ;) (I guess David Li, not me)
>>>>>>
>>>>>
>>>>> Nope, paragraph 2 from your original email.
>>>>>
>>>>>
>>>>>> I think maybe what could be worth doing would be
separating out the
>>>>>> broader/intentionally "end to end" sort of
tests from the ones intended to
>>>>>> test compiler-rt in relative isolation.
>>>>>>
>>>>>
>>>>> It's really hard to draw the line here, even some of
compiler-rt unit
>>>>> tests require instrumentation, therefore depend on new
features of
>>>>> Clang/LLVM. Unlike builtins, which are
>>>>> trivial to test in isolation, testing sanitizer runtimes in
isolation
>>>>> (w/o compiler) is often hard to implement (we tried to do
so for TSan, but
>>>>> found unit tests extremely hard to write),
>>>>> and is barely useful - compiler-rt runtimes don't
consist of modules
>>>>> (like LLVMCodeGen and LLVMMC for instance), and are never
used w/o the
>>>>> compiler anyway.
>>>>>
>>>>>
>>>>>>
>>>>>> Most importantly, I'd expect only the latter to run
in a "make
>>>>>> check-all" run, as we do for Clang/LLVM, etc.
>>>>>>
>>>>>
>>>>> And now we're getting to the goals :) Why would such a
change be good?
>>>>> Do you worry about the time it takes to execute the test
suite?
>>>>>
>>>>>
>>>>>>
>>>>>>
>>>>>>> Also, there's significant complexity in
compiler-rt test suite that
>>>>>>> narrows the tests executed
>>>>>>> to those supported by current host.
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> On Wed, Feb 10, 2016 at 2:33 PM, Xinliang David Li
via cfe-dev <
>>>>>>> cfe-dev at lists.llvm.org> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Wed, Feb 10, 2016 at 2:11 PM, Justin Bogner
via llvm-dev <
>>>>>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>>>>
>>>>>>>>> David Blaikie via cfe-dev <cfe-dev at
lists.llvm.org> writes:
>>>>>>>>> > Recently had a bit of a digression in
a review thread related to
>>>>>>>>> some tests
>>>>>>>>> > going in to compiler-rt (
>>>>>>>>> >
>>>>>>>>>
http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20160208/330759.html
>>>>>>>>> > ) and there seems to be some
disconnect at least between my
>>>>>>>>> expectations
>>>>>>>>> > and reality. So I figured I'd have
a bit of a discussion out
>>>>>>>>> here on the
>>>>>>>>> > dev lists where there's a bit more
visibility.
>>>>>>>>> >
>>>>>>>>> > My basic expectation is that the lit
tests in any LLVM project
>>>>>>>>> except the
>>>>>>>>> > test-suite are targeted tests intended
to test only the
>>>>>>>>> functionality in
>>>>>>>>> > the project. This seems like a pretty
well accepted doctrine
>>>>>>>>> across most
>>>>>>>>> > LLVM projects - most visibly in Clang,
where we make a concerted
>>>>>>>>> effort not
>>>>>>>>> > to have tests that execute LLVM
optimizations, etc.
>>>>>>>>> >
>>>>>>>>> > There are exceptions/middle ground to
this - DIBuilder is in
>>>>>>>>> LLVM, but
>>>>>>>>> > essentially tested in Clang rather
than writing LLVM unit tests.
>>>>>>>>> It's
>>>>>>>>> > somewhat unavoidable that any of the
IR building code (IRBuilder,
>>>>>>>>> > DIBuilder, IR asm printing, etc) is
'tested' incidentally in
>>>>>>>>> Clang in
>>>>>>>>> > process of testing Clang's IR
generation. But these are seen as
>>>>>>>>> incidental,
>>>>>>>>> > not intentionally trying to cover LLVM
with Clang tests (we
>>>>>>>>> don't add a
>>>>>>>>> > Clang test if we add a new feature to
IRBuilder just to test the
>>>>>>>>> IRBuilder).
>>>>>>>>> >
>>>>>>>>> > Another case with some middle ground
are things like linker
>>>>>>>>> tests and
>>>>>>>>> > objdump, dwarfdump, etc - in theory to
isolate the test we would
>>>>>>>>> checkin
>>>>>>>>> > binaries (or the textual object
representation lld had for a
>>>>>>>>> while, etc) to
>>>>>>>>> > test those tools. Some tests instead
checkin assembly and
>>>>>>>>> assemble it with
>>>>>>>>> > llvm-mc. Again, not to cover llvm-mc,
but on the assumption that
>>>>>>>>> llvm-mc is
>>>>>>>>> > tested, and just using it as a tool to
make tests easier to
>>>>>>>>> maintain.
>>>>>>>>> >
>>>>>>>>> > So I was surprised to find that the
compiler-rt lit tests seem
>>>>>>>>> to diverge
>>>>>>>>> > from this philosophy & contain
more intentional end-to-end tests
>>>>>>>>> (eg:
>>>>>>>>> > adding a test there when making a fix
to Clang to add a counter
>>>>>>>>> to a
>>>>>>>>> > function that was otherwise missing a
counter - I'd expect that
>>>>>>>>> to be
>>>>>>>>> > tested in Clang and that there would
already be coverage in
>>>>>>>>> compiler-rt for
>>>>>>>>> > "if a function has a counter,
does compiler-rt do the right
>>>>>>>>> thing with that
>>>>>>>>> > counter" (testing whatever code
in compiler-rt needs to be
>>>>>>>>> tested)).
>>>>>>>>> >
>>>>>>>>> > Am I off base here? Are
compiler-rt's tests fundamentally
>>>>>>>>> different to the
>>>>>>>>> > rest of the LLVM project? Why? Should
they continue to be?
>>>>>>>>>
>>>>>>>>> I think there's a bit of grey area in
terms testing the runtime -
>>>>>>>>> generally it's pretty hard to use the
runtime without a fairly
>>>>>>>>> end-to-end test, so tests of the runtime
often end up looking
>>>>>>>>> pretty
>>>>>>>>> close to an end-to-end test.
>>>>>>>>>
>>>>>>>>> That said, I don't think that should be
used as an excuse to sneak
>>>>>>>>> arbitrary end-to-end tests into
compiler-rt. We should absolutely
>>>>>>>>> write
>>>>>>>>> tests in clang and llvm that we're
inputting what we expect to the
>>>>>>>>> runtime and try to keep the tests in
compiler-rt as focused on just
>>>>>>>>> exercising the runtime code as possible.
>>>>>>>>>
>>>>>>>>
>>>>>>>> Yes, we should not use compiler-rt tests as an
excuse of not adding
>>>>>>>> clang/LLVM test. The latter should always be
added if possible -- they are
>>>>>>>> platform independent and is the first level of
defense.  runtime test's
>>>>>>>> focus is also more on the runtime lib itself
and interaction between
>>>>>>>>  runtime, compiler, binutils and other tools.
>>>>>>>>
>>>>>>>> David
>>>>>>>>
>>>>>>>>>
>>>>>>>>> IIUC, the correct place for integration
tests in general is
>>>>>>>>> somewhere
>>>>>>>>> like test-suite, but I think it's a bit
intimidating to some
>>>>>>>>> people to
>>>>>>>>> add new tests there (Are there docs on
this?). I suspect some of
>>>>>>>>> the
>>>>>>>>> profiling related tests in compiler-rt are
doing a bit much and
>>>>>>>>> should
>>>>>>>>> graduate to a spot in the test-suite (but I
don't have time to
>>>>>>>>> volunteer
>>>>>>>>> to do the work, unfortunately).
>>>>>>>>>
_______________________________________________
>>>>>>>>> LLVM Developers mailing list
>>>>>>>>> llvm-dev at lists.llvm.org
>>>>>>>>>
http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> cfe-dev mailing list
>>>>>>>> cfe-dev at lists.llvm.org
>>>>>>>>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Alexey Samsonov
>>>>>>> vonosmas at gmail.com
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> cfe-dev mailing list
>>>>>>> cfe-dev at lists.llvm.org
>>>>>>>
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Alexey Samsonov
>>>>> vonosmas at gmail.com
>>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> cfe-dev mailing list
>>>> cfe-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>>
>>>>
>>>
>>
>
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