[llvm-bugs] [Bug 46591] New: load-store-vectorizer cannot assume that offset calculated from add nuw is safe

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46591

            Bug ID: 46591
           Summary: load-store-vectorizer cannot assume that offset
                    calculated from add nuw is safe
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: juneyoung.lee at sf.snu.ac.kr
                CC: llvm-bugs at lists.llvm.org

Created attachment 23680
  --> https://bugs.llvm.org/attachment.cgi?id=23680&action=edit
Input & output

test/Transforms/LoadStoreVectorizer/X86/vectorize-i8-nested-add.ll 's
ld_v4i8_add_nuw vectorizes a sequence of loads, which is illegal.

https://godbolt.org/z/NzK5oY
(the attached file contains this input/output)

Counter example: if v0 and v1 is 0, nuw is never triggered, but the offsets
aren't still consecutive.
https://alive2.llvm.org/ce/z/4nZKBs

This can happen when a program has an allocation larger than 4G.

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20200705/19fc782c/attachment-0001.html>