[llvm] Rebased save csr in ra (PR #131845)

[Michael Maitland via llvm-commits]

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@@ -786,6 +788,153 @@ void RISCVFrameLowering::allocateStack(MachineBasicBlock &MBB,
   }
 }
 
+struct CFIBuildInfo {
+  MachineBasicBlock *MBB;
+  MachineInstr *InsertAfterMI; // nullptr means insert at MBB.begin()
+  DebugLoc DL;
+  unsigned CFIIndex;
+};
+
+static void trackRegisterAndEmitCFIs(
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michaelmaitland wrote:

Can you help me understand what this function is doing. Why is it needed? How does it work?

https://github.com/llvm/llvm-project/pull/131845