1. [DWARFYAML] Make the debug_str section optional. (details)
  2. [MemorySSA] Clean up single value phis. (details)
Commit 428b2ffad4a346a967a4a105356fbc0fa518e2cc by Xing
[DWARFYAML] Make the debug_str section optional.

This patch makes the debug_str section optional. When the debug_str
section exists but doesn't contain anything, yaml2obj will emit a
section header for it.

Reviewed By: grimar

Differential Revision:
The file was modifiedllvm/lib/ObjectYAML/DWARFYAML.cpp
The file was modifiedllvm/include/llvm/ObjectYAML/DWARFYAML.h
The file was modifiedllvm/lib/ObjectYAML/DWARFEmitter.cpp
The file was modifiedllvm/test/ObjectYAML/MachO/DWARF-debug_str.yaml
The file was modifiedllvm/tools/obj2yaml/dwarf2yaml.cpp
The file was modifiedllvm/test/tools/yaml2obj/ELF/DWARF/debug-str.yaml
Commit 63844c116a0acf8a75ebe4ed6f25fced3c655710 by asbirlea
[MemorySSA] Clean up single value phis.

MemoryPhis with a single value are correct, but can lead to errors when
updating. Clean up single entry Phis newly added when cloning blocks.
Resolves PR46574.
The file was modifiedllvm/lib/Analysis/MemorySSAUpdater.cpp
The file was addedllvm/test/Analysis/MemorySSA/pr46574.ll