[llvm-bugs] [Bug 30806] Wrong code generation at -O2 leading to division by zero

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=30806

Warren Ristow <warren_ristow at playstation.sony.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |---
 Fixed By Commit(s)|r347934                     |

--- Comment #17 from Warren Ristow <warren_ristow at playstation.sony.com> ---
(In reply to Warren Ristow from comment #16)
> 
> The patch has landed:
> https://reviews.llvm.org/rL347934

I'm re-opening, as this patch was reverted at:
https://reviews.llvm.org/rL348426

The problem is SEGVs in PHINode simplification in instcombine, as described in
the llvm-commits thread for r347934.

---------------------------------------------------------

As an aside, as discussed in the review:
https://reviews.llvm.org/D55232

(for a related patch, to fix bug 38697), in studying the history of the code in
this area, I noticed that a similar fix was made about a year ago at r289412.
But that year-old fix was reverted at r289453, with the following note:

  Reverts r289412. It caused an OOB PHI operand access in instcombine when
  ASan is enabled. Reduction in progress.

It may be that the SEGVs in PHINode simplification that motivated the revert
for the new patch are rooted in the same problem that motivated the revert that
was done a year ago.

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