[Bug tree-optimization/126225] New: [12/13/14/15/16/17 Regression] Wrong code at -O2 due to incorrect SLP IV reuse

[cemakgok at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126225

            Bug ID: 126225
           Summary: [12/13/14/15/16/17 Regression] Wrong code at -O2 due
                    to incorrect SLP IV reuse
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: cemakgok at gmail dot com
  Target Milestone: ---

Created attachment 65014
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65014&action=edit
Reduced testcase

Godbolt: https://godbolt.org/z/Mbohx7sEn

Wrong code at -O2.
All major versions from 11 to trunk affected. (11 miscompiles at -O3 only)
Compiles correctly with -fno-tree-loop-vectorize.

Bisected to: 092cdbd9198497593fb034971d0f80fc931ab145
("Re-instantiate SLP induction IV CSE")

Vectorizer reuses induction variables across multiple SLP lanes without actualy
verifying that the lanes share the same scalar values.
Sent a patch for it.