[all-commits] [llvm/llvm-project] 282ec4: [ValueTracking] A value is never undef or poison i...

[Juneyoung Lee via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 282ec40504369e6533e03d7690417feb0da8cdd4
      https://github.com/llvm/llvm-project/commit/282ec40504369e6533e03d7690417feb0da8cdd4
  Author: Juneyoung Lee <aqjune at gmail.com>
  Date:   2020-03-01 (Sun, 01 Mar 2020)

  Changed paths:
    M llvm/lib/Analysis/ValueTracking.cpp

  Log Message:
  -----------
  [ValueTracking] A value is never undef or poison if it must raise UB

Summary:
This patch helps isGuaranteedNotToBeUndefOrPoison return true if the value
makes the program always undefined.

According to value tracking functions' comments, it is not still in consensus
whether a poison value can be bitwise or not, so conservatively only the case with
i1 is considered.

Reviewers: spatel, lebedev.ri, reames, nlopes, regehr

Reviewed By: nlopes

Subscribers: uenoku, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75396