[llvm] [RISCV][WIP] Let RA do the CSR saves. (PR #90819)

[Mikhail Gudim via llvm-commits]

================
@@ -21874,6 +21874,108 @@ bool RISCVTargetLowering::fallBackToDAGISel(const Instruction &Inst) const {
   return false;
 }
 
+static MachineInstr *findInstrWhichNeedAllCSRs(MachineBasicBlock &MBB) {
+  // Some instructions may require (implicitly) all CSRs to be saved.
----------------
mgudim wrote:

I don't know how we can solve this more generally. Maybe we can introduce a new attribute?

https://github.com/llvm/llvm-project/pull/90819