[llvm] [llvm] Support multiple save/restore points in mir (PR #119357)

[Michael Maitland via llvm-commits]

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@@ -478,12 +478,59 @@ bool RISCVRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
   MachineInstr &MI = *II;
   MachineFunction &MF = *MI.getParent()->getParent();
   MachineRegisterInfo &MRI = MF.getRegInfo();
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
   DebugLoc DL = MI.getDebugLoc();
 
   int FrameIndex = MI.getOperand(FIOperandNum).getIndex();
   Register FrameReg;
   StackOffset Offset =
       getFrameLowering(MF)->getFrameIndexReference(MF, FrameIndex, FrameReg);
+
+  const auto &CSI =
+      getFrameLowering(MF)->getUnmanagedCSI(MF, MFI.getCalleeSavedInfo());
+
+  if (!CSI.empty()) {
+    int MinCSFI = CSI.front().getFrameIdx();
+    int MaxCSFI = CSI.back().getFrameIdx();
+
+    // If our FrameIndex is CSI FrameIndex we in some cases need additional
+    // adjustment
+    if (FrameIndex >= MinCSFI && FrameIndex <= MaxCSFI) {
+      MachineBasicBlock *SpilledIn = nullptr;
+      MachineBasicBlock *RestoredIn = nullptr;
+      auto It = std::find_if(CSI.begin(), CSI.end(), [FrameIndex](auto &CS) {
+        return CS.getFrameIdx() == FrameIndex;
+      });
+
+      if (It != CSI.end()) {
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michaelmaitland wrote:

IS it possible for this condition to be false? If so, will SpilledIn and RestoredIn be nullptr below? I think that would be an issue. If it cannot be false, maybe we should drop the `if` statement here.

https://github.com/llvm/llvm-project/pull/119357