[llvm] Add FeatureFuseLiterals as SubTargetFeature for Grace and Olympus (PR #160257)

[Sushant Gokhale via llvm-commits]

sushgokh wrote:

> Can you provide an example of the function this help with? You said it was something in povray? I'm wondering if it is something we can fix more directly. Why are we hoisting a constant into the entry block off a function that can otherwise be shrink-wrapped? Why does a load from a constant pool block shrink wrapping?

It is not constant load being shrink wrapped. There are 2 things happening here:
1. adrp+ldr sequence being converted to mov's+fmov 
2. shrink wrapping. This is not of the above ldr in (1).  Its enabling shrink wrapping of Callee saved registers and other stuff which was not happening otherwise.

(1) and (2) are unrelated in this sense. 

https://github.com/llvm/llvm-project/pull/160257