[LLVMbugs] [Bug 16455] New: loop vectorizer miscompile (t10135 case from PR16431)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=16455

            Bug ID: 16455
           Summary: loop vectorizer miscompile (t10135 case from PR16431)
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Loop Optimizer
          Assignee: unassignedbugs at nondot.org
          Reporter: hfinkel at anl.gov
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 10767
  --> http://llvm.org/bugs/attachment.cgi?id=10767&action=edit
bugpoint reduced test case and input file

The loop vectorizer miscompiles the attached input (there is an input text file
read by the program which demonstrates the problem). This is the t10135 case
from PR16431.

Specifically, if you run:
opt -loop-vectorize -mcpu=x86-64 bugpoint-passinput.ll

Then the resulting program outputs:
res = 3453

whereas compiling it without running the loop vectorizer, the resulting program
outputs:
res = 5321

Unfortunately, bugpoint crashes when attempting to further reduce the test case
:(
 -- but at least it was able to isolate the relevant pass.

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