1. [X86] Disable rematerializion for PTILELOADDV (details)
  2. [SimplifyCFG] avoid illegal phi with both poison and undef (details)
Commit 42e025f9deab39717738e98309370c6df851b1c6 by
[X86] Disable rematerializion for PTILELOADDV

Per the discussion in D97453. We currently disable it due to it's not a
common scenario and has some problem in implementation.

Differential Revision:
The file was modifiedllvm/lib/Target/X86/
The file was modifiedllvm/lib/Target/X86/X86InstrInfo.cpp
The file was modifiedllvm/test/CodeGen/X86/AMX/amx-across-func.ll
Commit 356cdabd3a9e0ff919ea2c1a35c8706ecb915297 by spatel
[SimplifyCFG] avoid illegal phi with both poison and undef

In the example based on:
...we are crashing because poison is a subclass of undef, so we merge blocks and create:

PHI node has multiple entries for the same basic block with different incoming values!
  %k3 = phi i64 [ poison, %entry ], [ %k3, %g ], [ undef, %entry ]

If both poison and undef values are incoming, we soften the poison values to undef.

Differential Revision:
The file was addedllvm/test/Transforms/SimplifyCFG/poison-merge.ll
The file was modifiedllvm/lib/Transforms/Utils/Local.cpp