[llvm] r240291 - Fix shl folding in DAG combiner.

[Paweł Bylica]

Reverted in r240343. I'm finishing for today. Sorry for the troubles, but
it's quite a surprise for me.

How can I reproduce the problem locally?

On Mon, Jun 22, 2015 at 11:38 PM Frédéric Riss <friss at apple.com> wrote:

> On Jun 22, 2015, at 1:57 PM, Paweł Bylica <chfast at gmail.com> wrote:
>
> I'm about to send a change that will fix the regression test (it should be
> -march=x86). It should fix build failures like:
> http://lab.llvm.org:8011/builders/llvm-s390x-linux1/builds/16458
>
> However your is similar to that one:
>
> http://lab.llvm.org:8011/builders/clang-x86_64-linux-selfhost-abi-test/builds/5852
> but I'm not sure what's wrong with that.
>
> Give me 10 more minutes. If it will not help, please revert it.
>
>
> I just saw your commit. I think there is no way that your fix in the test
> could fix any of the self host issues (the green dragon failure is a
> self-hosted LTO build and the other failing bot you pointed me at is also a
> self-host). Are you investigating the other failures? The 2 failing bots
> have only your commit in common in their blame lists so at this point it’s
> pretty clear that this commit triggers something very wrong in a clang
> self-host build. It  should be pretty easy to reproduce. I’d appreciate if
> you revert this change so that the bots can become green again.
>
> Fred
>
> - Paweł
>
>
>
> On Mon, Jun 22, 2015 at 10:47 PM Frédéric Riss <friss at apple.com> wrote:
>
>> This commit is by far the most likely culprit for the hangs we see on
>> green dragon:
>> http://lab.llvm.org:8080/green/job/clang-stage2-configure-Rlto_check/
>>
>> Did you have any other failures? Would you mind reverting it to see if it
>> fixes things? (This is after an LTO bootstrap, so it takes quite some time
>> to reproduce/propagate).
>>
>> Fred
>>
>> On Jun 22, 2015, at 8:58 AM, Pawel Bylica <chfast at gmail.com> wrote:
>>
>> Author: chfast
>> Date: Mon Jun 22 10:58:11 2015
>> New Revision: 240291
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=240291&view=rev
>> Log:
>> Fix shl folding in DAG combiner.
>>
>> Summary: The code responsible for shl folding in the DAGCombiner was
>> assuming incorrectly that all constants are less than 64 bits. This patch
>> simply changes the way values are compared.
>>
>> Test Plan: A regression test included.
>>
>> Reviewers: andreadb
>>
>> Reviewed By: andreadb
>>
>> Subscribers: andreadb, test, llvm-commits
>>
>> Differential Revision: http://reviews.llvm.org/D10602
>>
>> Added:
>>    llvm/trunk/test/CodeGen/X86/fold-vector-shl-crash.ll
>> Modified:
>>    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>>
>> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=240291&r1=240290&r2=240291&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Mon Jun 22
>> 10:58:11 2015
>> @@ -4275,7 +4275,7 @@ SDValue DAGCombiner::visitSHL(SDNode *N)
>>   if (isNullConstant(N0))
>>     return N0;
>>   // fold (shl x, c >= size(x)) -> undef
>> -  if (N1C && N1C->getZExtValue() >= OpSizeInBits)
>> +  if (N1C && N1C->getAPIntValue().uge(OpSizeInBits))
>>     return DAG.getUNDEF(VT);
>>   // fold (shl x, 0) -> x
>>   if (N1C && N1C->isNullValue())
>>
>> Added: llvm/trunk/test/CodeGen/X86/fold-vector-shl-crash.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/fold-vector-shl-crash.ll?rev=240291&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/test/CodeGen/X86/fold-vector-shl-crash.ll (added)
>> +++ llvm/trunk/test/CodeGen/X86/fold-vector-shl-crash.ll Mon Jun 22
>> 10:58:11 2015
>> @@ -0,0 +1,8 @@
>> +; RUN: llc < %s | FileCheck %s
>> +
>> +;CHECK-LABEL: test
>> +define <2 x i256> @test() {
>> +  %S = shufflevector <2 x i256> zeroinitializer, <2 x i256> <i256 -1,
>> i256 -1>, <2 x i32> <i32 0, i32 2>
>> +  %B = shl <2 x i256> %S, <i256 -1, i256 -1> ; DAG Combiner crashes here
>> +  ret <2 x i256> %B
>> +}
>>
>>
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>>
>>
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