[Bug tree-optimization/79824] New: [7 Regression] Failure to peel for gaps leads to read beyond mapped memory

[rsandifo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79824

            Bug ID: 79824
           Summary: [7 Regression] Failure to peel for gaps leads to read
                    beyond mapped memory
           Product: gcc
           Version: 7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rsandifo at gcc dot gnu.org
  Target Milestone: ---

Created attachment 40876
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40876&action=edit
Testcase

After r241959 we avoid peeling for gaps if the vector is aligned.  That isn't
safe because the gap itself could be vector-sized or wider.

The attached testcase is based on pr49038.c and uses Richard's suggestion of
__builtin_assumed_aligned.