[llvm] [CGP] Consider arguments and ret values in `dupRetToEnableTailCallOpts` (PR #76613)

[David Li via llvm-commits]

david-xl wrote:

> > Can you provide any performance numbers (real applications, benchmark suite) etc?
> 
> What will depend on these numbers? Do you mean that we don't merge this if it's not possible to demonstrate the effect? Obtaining relativistic performance data for smaller improvements is usually very expensive, and not possible to do an improvement less than 0.1%.

It is the other way around. Having some positive numbers will help speed up the approval. There are always trade-offs between runtime performance and compile time overhead (probably not a concern for this case).

There is also chance of trigging unexpected regressions. Having some test coverage gives people more confidence.

Having said that, this patch LGTM.

https://github.com/llvm/llvm-project/pull/76613