[llvm-bugs] [Bug 43188] Incorrect fold of uadd.with.overflow with undef

via llvm-bugs llvm-bugs at lists.llvm.org
Sun Sep 1 05:31:07 PDT 2019


Nuno Lopes <nunoplopes at sapo.pt> changed:

           What    |Removed                     |Added
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |---

--- Comment #5 from Nuno Lopes <nunoplopes at sapo.pt> ---
I've just added support for struct consts in Alive2, so we can verify these now
We now get:
define {i8, i1} @uadd_undef() {
  %t = uadd_overflow i8 142, undef
  ret {i8, i1} %t
define {i8, i1} @uadd_undef() {
  ret {i8, i1} { undef, 0 }

This is still incorrect. It has to be { undef, 1 }.  You cannot get, for
example, {0, 0} in the original program, while the optimized one can produce

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