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

[Paweł Bylica]

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.

- 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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