[LLVMbugs] [Bug 22225] New: Spec2006 403.gcc misscompare runfail with avx512 loop vectorization

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=22225

            Bug ID: 22225
           Summary: Spec2006 403.gcc misscompare runfail with avx512 loop
                    vectorization
           Product: tools
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: opt
          Assignee: unassignedbugs at nondot.org
          Reporter: sgvozdar at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Test 403.gcc from spec2006 started to fail after a commit:

commit 14fb445715551c6eda9146e829d0470550c8fff6
Author: Elena Demikhovsky <elena.demikhovsky at intel.com>
Date:   Tue Dec 16 11:50:42 2014 +0000

    Masked Load and Store Intrinsics in loop vectorizer.
    The loop vectorizer optimizes loops containing conditional memory
    accesses by generating masked load and store intrinsics.
    This decision is target dependent.

    http://reviews.llvm.org/D6527

Compiler options:
-O2 -ffast-math -static -m32 -mfpmath=sse -march=core-avx2

On -march=slm this test is OK.


LOG:
...
*** Miscompare of 166.s;
32309:          movq    %rbx, %rdi
                movl    $1, %r9d
            ^
32311:          movl    $.LC154, %esi
                movq    %rbx, %rdi
            ^
32312:          movl    $.LC155, %edx
                movl    $.LC154, %esi
                    ^
32313:          movl    $max_insts, %ecx
                movl    $.LC155, %edx
               ^
32314:          movl    $1, %r9d
                movl    $max_insts, %ecx
               ^
32318:          xorl    %r8d, %r8d
                movl    $.LC156, %esi
         ^
32319:          movl    $.LC156, %esi
                movl    $.LC157, %edx
                    ^
32320:          movl    $.LC157, %edx
                movl    $fastfwd_count, %ecx
               ^
32321:          movl    $fastfwd_count, %ecx
                movq    $0, (%rsp)
            ^
32322:          movl    $1, %r9d
                call    opt_reg_int
         ^

Sergey Gvozdarev
===============
Software Engineer
Intel Compiler Team
Intel

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