[all-commits] [llvm/llvm-project] bfd2c2: [IR][LoopRotate] avoid leaving phi with no operand...

[RotateRight via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: bfd2c216ea8ef09f8fb1f755ca2b89f86f74acbb
      https://github.com/llvm/llvm-project/commit/bfd2c216ea8ef09f8fb1f755ca2b89f86f74acbb
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2020-11-30 (Mon, 30 Nov 2020)

  Changed paths:
    M llvm/include/llvm/IR/BasicBlock.h
    M llvm/lib/IR/BasicBlock.cpp
    A llvm/test/Transforms/LoopRotate/phi-empty.ll

  Log Message:
  -----------
  [IR][LoopRotate] avoid leaving phi with no operands (PR48296)

https://llvm.org/PR48296 shows an example where we delete all of the operands
of a phi without actually deleting the phi, and that is currently considered
invalid IR. The reduced test included here would crash for that reason.

A suggested follow-up is to loosen the assert to allow 0-operand phis
in unreachable blocks.

Differential Revision: https://reviews.llvm.org/D92247