[llvm] r226490 - IR: Remove direct comparisons against Metadata::Storage, NFC

Timur Iskhodzhanov timurrrr at google.com
Tue Jan 20 08:38:26 PST 2015 

On Tue Jan 20 2015 at 6:58:52 PM Duncan P. N. Exon Smith <
dexonsmith at apple.com> wrote:

> > On 2015 Jan 20, at 07:53, Timur Iskhodzhanov <timurrrr at google.com>
> wrote:
> >
> > This is what I get on my Windows machine:
> >   $ cat test.cpp
> >   char hello;
> >   $ bin\clang.exe -cc1 -gline-tables-only -triple i686-pc-linux
> -emit-obj -o z test.cpp
> >   Assertion failed: DbgNode->isTemporary() && "Expected temporary node",
> file ..\lib\IR\DebugInfo.cpp, line 350
> > but on Linux it's fine.
> >
> > Replacing
> >   StorageType Storage : 2;
> > with
> >   unsigned Storage : 2;
> > seems to resolve the issue.
> > Shall I commit this change?
> >
>
> Thanks for tracking this down!
>

You've just won a black belt in remote debugging :)


> I guessed at the same thing and got someone on IRC to confirm.  Already
> committed in r226570.
>

Thanks, the Chromium bots are cycling green now!

> Reid might know the enum stuff better.
>
> It's not an enum problem, as it turns out.  Same difference in behaviour
> would happen with `int Storage : 2`.
>
> MSVC makes the top bit of the bitfield the sign bit; other compilers
> "chop off" the sign bit.  It's implementation-defined which behaviour
> you get (so MSVC isn't actually wrong here, just annoyingly different).
>
> I should have remembered this :/.  Sorry for the trouble.
>

Do you think we could somehow find such bugs automatically?
And/or update the developer policy?

> On Tue Jan 20 2015 at 6:39:22 PM Duncan P. N. Exon Smith <
> dexonsmith at apple.com> wrote:
> >
> > > On 2015 Jan 20, at 07:32, Timur Iskhodzhanov <timurrrr at google.com>
> wrote:
> > >
> > >
> > >
> > > On Tue Jan 20 2015 at 6:20:34 PM Duncan Exon Smith <
> dexonsmith at apple.com> wrote:
> > >
> > >
> > > On Jan 20, 2015, at 3:48 AM, Timur Iskhodzhanov <timurrrr at google.com>
> wrote:
> > >
> > >> Hi Duncan,
> > >>
> > >> This has broken down "ninja check-asan" on 32-bit Windows.
> > >> Assertion failed: Context.hasReplaceableUses() && "Expected RAUW
> support", file C:\src\llvm_bot\slave\win\build\llvm\include\llvm/IR/Metadata.h,
> line 976
> > >
> > > Can you include the asan output?   A backtrace?   Point at a
> buildbot?   I don't have the tools to reproduce this.
> > >
> > > There's no public buildbot for ASan itself, but turns out this problem
> is not even specific to ASan.
> > >
> > > This public bot just builds Chromium with Clang
> > > http://build.chromium.org/p/chromium.fyi/builders/
> CrWinClang/builds/1295/steps/compile/logs/stdio
> > >
> > > Assertion failed: isTemporary() && "Expected temporary node", file
> C:\b\build\slave\CrWinClang\build\src\third_party\llvm\include\llvm/IR/Metadata.h,
> line 741
> > > since r226499.
> > >
> > > OK, I'll try to minimize...
> > > (I suppose the change looks sane at the first glance and you can't
> come up with a repro yourself)
> > >
> > > It seems to be hard to revert now...
> > >> You've committed a lot of small changes in a very short timeframe -
> > >
> > > Actually, I committed work over the span of an entire work day.
> > >
> > > Oh, I see.
> > >> - I assume you're using git?  Is there a reason why you don't squash
> your changes before committing?  It makes finding bad commits / reverting
> harder...
> > >
> > > Besides being developer policy to separate changes as much as
> possible, it also makes changes easier to review, and isolating which
> change causes a problem easier to determine.
> > >
> > > Unless it results in complex history and back-in-forth changes, I
> suppose.
> > > I've spent more than an hour today trying to locally bisect and revert
> the changes and ended up just locally reverting 40+ of your commits after
> 226490 to make progress.  Unfortunately, reverting just r226490 results in
> a waterfall of merge conflicts.
> >
> > Yup, all the others depend on it.  I would have dealt with it myself
> > if a buildbot had told me about it.
> >
> > > Do you think it's reasonable to temporarily revert your changes in the
> [r226490, HEAD] range to unbreak stuff?
> > > I have a patch ready for that.
> >
> > Certainly an option, although I'm actively looking at this right now
> > (sorry for the delay, I'm in PDT so I just woke up).
> >
> > Did you do a full bisect?  Are you sure that leaving this in and
> > reverting the ones that follow don't also fix it?
> >
> > Do you know if MSVC handles things like:
> >
> >     enum StorageType { ... };
> >     StorageType Storage : 2;
> >
> > correctly (well, the way I expect), or should I store it as an
> >
> >     unsigned Storage : 2;
> >
> > for compatibility?  Any chance it causes a weird layout problem that
> > this commit happens to point out?
> >
> > (Given that this is MSVC-only, I suspect there's a layout problem or
> > UB somewhere.)
> >
> > >> On Mon Jan 19 2015 at 10:30:36 PM Duncan P. N. Exon Smith <
> dexonsmith at apple.com> wrote:
> > >> Author: dexonsmith
> > >> Date: Mon Jan 19 13:26:24 2015
> > >> New Revision: 226490
> > >>
> > >> URL: http://llvm.org/viewvc/llvm-project?rev=226490&view=rev
> > >> Log:
> > >> IR: Remove direct comparisons against Metadata::Storage, NFC
> > >>
> > >> Modified:
> > >>     llvm/trunk/lib/IR/Metadata.cpp
> > >>
> > >> Modified: llvm/trunk/lib/IR/Metadata.cpp
> > >> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/
> Metadata.cpp?rev=226490&r1=226489&r2=226490&view=diff
> > >> ============================================================
> ==================
> > >> --- llvm/trunk/lib/IR/Metadata.cpp (original)
> > >> +++ llvm/trunk/lib/IR/Metadata.cpp Mon Jan 19 13:26:24 2015
> > >> @@ -402,7 +402,7 @@ MDNode::MDNode(LLVMContext &Context, uns
> > >>    for (unsigned I = 0, E = MDs.size(); I != E; ++I)
> > >>      setOperand(I, MDs[I]);
> > >>
> > >> -  if (Storage == Temporary)
> > >> +  if (isTemporary())
> > >>      this->Context.makeReplaceable(
> > >>          make_unique<ReplaceableMetadataImpl>(Context));
> > >>  }
> > >> @@ -416,7 +416,7 @@ static bool isOperandUnresolved(Metadata
> > >>  UniquableMDNode::UniquableMDNode(LLVMContext &C, unsigned ID,
> > >>                                   StorageType Storage,
> ArrayRef<Metadata *> Vals)
> > >>      : MDNode(C, ID, Storage, Vals) {
> > >> -  if (Storage != Uniqued)
> > >> +  if (!isUniqued())
> > >>      return;
> > >>
> > >>    // Check whether any operands are unresolved, requiring
> re-uniquing.
> > >> @@ -432,7 +432,7 @@ UniquableMDNode::UniquableMDNode(LLVMCon
> > >>  }
> > >>
> > >>  void UniquableMDNode::resolve() {
> > >> -  assert(Storage == Uniqued && "Expected this to be uniqued");
> > >> +  assert(isUniqued() && "Expected this to be uniqued");
> > >>    assert(!isResolved() && "Expected this to be unresolved");
> > >>
> > >>    // Move the map, so that this immediately looks resolved.
> > >>
> > >>
> > >> _______________________________________________
> > >> llvm-commits mailing list
> > >> llvm-commits at cs.uiuc.edu
> > >> http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
> >
>
>
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