[llvm] [RISCV] Add branch+c.mv macrofusion for sifive-p450. (PR #76169)

[Philip Reames via llvm-commits]

================
@@ -996,6 +996,12 @@ def TuneShortForwardBranchOpt
 def HasShortForwardBranchOpt : Predicate<"Subtarget->hasShortForwardBranchOpt()">;
 def NoShortForwardBranchOpt : Predicate<"!Subtarget->hasShortForwardBranchOpt()">;
 
+def TuneCMOVBranchOpt
----------------
preames wrote:

This naming is hard for me to parse at a glance.  A couple ideas:
* TuneCMovFusion
* TuneShortForwardBranchCMovOnly

https://github.com/llvm/llvm-project/pull/76169