1. [GlobalISel] Add a `X, Y = G_UNMERGE(G_ZEXT Z)` -> X = G_ZEXT Z; Y = 0 combine (details)
Commit b3afad046301d8bb1f4471aceaad704b87de3a69 by qcolombet
[GlobalISel] Add a `X, Y = G_UNMERGE(G_ZEXT Z)` -> X = G_ZEXT Z; Y = 0 combine

Add a combiner helper to transform unmerge of zext into one zext and
a constant 0

Differential Revision:
The file was modifiedllvm/include/llvm/CodeGen/GlobalISel/CombinerHelper.h (diff)
The file was modifiedllvm/include/llvm/Target/GlobalISel/ (diff)
The file was modifiedllvm/test/CodeGen/AMDGPU/GlobalISel/udiv.i32.ll (diff)
The file was modifiedllvm/test/CodeGen/AMDGPU/GlobalISel/urem.i32.ll (diff)
The file was modifiedllvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp (diff)
The file was modifiedllvm/test/CodeGen/AMDGPU/GlobalISel/srem.i32.ll (diff)
The file was modifiedllvm/test/CodeGen/AArch64/GlobalISel/combine-unmerge.mir (diff)
The file was modifiedllvm/test/CodeGen/AMDGPU/GlobalISel/sdiv.i32.ll (diff)
The file was modifiedllvm/test/CodeGen/AMDGPU/GlobalISel/shl-ext-reduce.ll (diff)