[llvm-bugs] [Bug 46455] New: SLP vectorizer miscompiles reduction

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46455

            Bug ID: 46455
           Summary: SLP vectorizer miscompiles reduction
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Loop Optimizer
          Assignee: unassignedbugs at nondot.org
          Reporter: benny.kra at gmail.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 23650
  --> https://bugs.llvm.org/attachment.cgi?id=23650&action=edit
Unreduced test case

Test case is a bit large and will probably only work on Skylake + Linux.

$ clang++ -O3 module_0000.ir-no-opt.ll driver.cc -march=skx && ./a.out
buffer-assignment.txt
Output:
(
2, 4
,
1, 2, 2, 2
)

$ clang++ -O3 module_0000.ir-no-opt.ll driver.cc -march=skx -mllvm
-vectorize-slp=false && ./a.out buffer-assignment.txt
Output:
(
3, 4
,
1, 2, 2, 2
)

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