[llvm] [LoongArch][GlobalISel] Adding initial GlobalISel infrastructure (PR #76912)

[Lu Weining via llvm-commits]

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+//===-- LoongArchCallLowering.cpp - Call lowering ---------------*- C++ -*-===//
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SixWeining wrote:

Since the filename is too generic, you can put this file and other files in a seperate sub-folder like `GISel`.

https://github.com/llvm/llvm-project/pull/76912