[llvm] [llvm][CodeGen] Add a new software pipeliner 'Window Scheduler' (PR #84443)

[Hua Tian via llvm-commits]

huaatian wrote:

> > > > @dtcxzyw hi，yingwei，looks like our multiple commits were not squashed together~
> > > 
> > > 
> > > Do you mean the commit message?
> > 
> > 
> > Yes，there are five commits here. Sorry for the trouble. <img alt="image" width="615" src="https://private-user-images.githubusercontent.com/142874007/339316791-e27cecef-8326-43cd-be90-43c86e805bdc.png?jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJnaXRodWIuY29tIiwiYXVkIjoicmF3LmdpdGh1YnVzZXJjb250ZW50LmNvbSIsImtleSI6ImtleTUiLCJleHAiOjE3MTgyNzM1ODEsIm5iZiI6MTcxODI3MzI4MSwicGF0aCI6Ii8xNDI4NzQwMDcvMzM5MzE2NzkxLWUyN2NlY2VmLTgzMjYtNDNjZC1iZTkwLTQzYzg2ZTgwNWJkYy5wbmc_WC1BbXotQWxnb3JpdGhtPUFXUzQtSE1BQy1TSEEyNTYmWC1BbXotQ3JlZGVudGlhbD1BS0lBVkNPRFlMU0E1M1BRSzRaQSUyRjIwMjQwNjEzJTJGdXMtZWFzdC0xJTJGczMlMkZhd3M0X3JlcXVlc3QmWC1BbXotRGF0ZT0yMDI0MDYxM1QxMDA4MDFaJlgtQW16LUV4cGlyZXM9MzAwJlgtQW16LVNpZ25hdHVyZT0yOGRhMmIxNzNhZjU3ZWM1YWVkOGI0MjJiYTE3NzgxOTJlZTcyZjAyZDhkNTUxZGMxYjJhMmI3YjM1NzMwZjA5JlgtQW16LVNpZ25lZEhlYWRlcnM9aG9zdCZhY3Rvcl9pZD0wJmtleV9pZD0wJnJlcG9faWQ9MCJ9.o3FDO497Ia-eKq2y5KLbm2_FhgNWVqV6JeaO7LqiCA8">
> 
> Emm, you need to update the PR description before requesting a merge :) Sorry about that.

Sorry for the trouble. How do you suggest we handle it now?

https://github.com/llvm/llvm-project/pull/84443