<html>
    <head>
      <base href="https://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - spec2000/188.ammp miscompare fail on IA64 HSW architecture after commit r260063"
   href="https://llvm.org/bugs/show_bug.cgi?id=26561">26561</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>spec2000/188.ammp miscompare fail on IA64 HSW architecture after commit r260063
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Backend: X86
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>sergey.k.okunev@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org, llvm-dev@redking.me.uk, sergey.k.okunev@gmail.com, sergos.gnu@gmail.com, spatel+llvm@rotateright.com, zia.ansari@intel.com
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Bisect analysis showed LLVM revision 260063 is responsible for the fail. The
comments to commit are the following.

commit 392b9d21fce095df29f5a549c4a7d9d59761b32f
Author: Simon Pilgrim <<a href="mailto:llvm-dev@redking.me.uk">llvm-dev@redking.me.uk</a>>
Date:   Sun Feb 7 22:51:06 2016 +0000

    [X86][SSE] Resolve target shuffle inputs to sentinels to permit more
combines

    The combineX86ShufflesRecursively only supports unary shuffles, but was
missing the opportunity to combine binary shuffles with a zero / undef second
input.

    This patch resolves target shuffle inputs, converting the shuffle mask
elements to SM_SentinelUndef/SM_SentinelZero where possible. It then resolves
the updated mask to check if we have created a faux unary shuffle.

    Additionally, we now attempt to recursively call
combineX86ShufflesRecursively for all input operands (we used to just recurse
for unary integer shuffles and unary unpacks) - it safely returns early if its
not a target shuffle.

    Differential Revision: <a href="http://reviews.llvm.org/D16683">http://reviews.llvm.org/D16683</a>

    git-svn-id: <a href="https://llvm.org/svn/llvm-project/llvm/trunk@260063">https://llvm.org/svn/llvm-project/llvm/trunk@260063</a>
91177308-0d34-0410-b5e6-96231b3b80d8


LLVM-clang options: -m64 -fuse-ld=gold -static -O2 -ffast-math -march=core-avx2 

The failure is reproduced in concurrent applying of “-ffast-math
-march=core-avx2” options only.
spec2000 harness gives the following miscompare message (file – ammp.out.cmp).

0012:   1183.095771 bond energy
        1036.076023 bond energy
                  ^
0013:   2140.779933 angle energy
        2049.475812 angle energy
                  ^
0014:   67.674876 hybrid energy
        63.753323 hybrid energy
                ^
0016:   -15738.937252 non-bonded energy
        -14111.964160 non-bonded energy
                    ^
0017:   -11819.178977 total potential energy
        -10434.282631 total potential energy
                    ^
0018:   8533.288451 total kinetic energy
        8588.981709 total kinetic energy
                  ^
0019:   -3285.890527 total energy
        -1845.300921 total energy
                   ^
0020:   20352.467428 total action
        19023.264340 total action
                   ^
0025:   1232.045367 bond energy
        1061.815654 bond energy
                  ^
0026:   2228.827988 angle energy
        2053.136001 angle energy
                  ^
0027:   69.507047 hybrid energy
        65.092695 hybrid energy


Okunev Sergey,
Software Engineer
Intel Compiler Team</pre>
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