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[Bug tree-optimization/71060] New: Compiler reports "loop vectorized" but actually it was not


https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71060

            Bug ID: 71060
           Summary: Compiler reports "loop vectorized" but actually  it
                    was not
           Product: gcc
           Version: 5.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: niva at niisi dot msk.ru
  Target Milestone: ---

Created attachment 38467
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38467&action=edit
The test case to reproduce the problem

I compile the attached test8.c as follows:

/usr/local/bin/gcc   -O3 -S -mavx -fopt-info-vec-optimized -DSCOUT -Wall
-Wextra -Werror -Wno-unknown-pragmas test8.c -o test8.s3

The output is:

test8.c:24:2: note: loop vectorized
test8.c:24:2: note: loop versioned for vectorization because of possible
aliasing

But the resulting assembler code contains no vector instructions. 

Other problems related to this test are:

1. The pointers in this function has the restrict specifier, so there should be
no loop versioning.

2. I tried to use -ftree-loop-if-convert-stores but it did not help.

Possibly this bug is the same as 65206.

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