[clang] [llvm] [RISCV] Support frame pointers in SiFive CLIC preemptible handlers (PR #221318)

[Sam Elliott via cfe-commits]

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@@ -1651,7 +1682,10 @@ RISCVFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
     MaxCSFI = std::max(CSI.front().getFrameIdx(), CSI.back().getFrameIdx());
   }
 
-  if (FI >= MinCSFI && FI <= MaxCSFI) {
+  bool IsInterruptCSR = RVFI->isSiFivePreemptibleInterrupt(MF) &&
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lenary wrote:

This sounds... bad. I guess no one was hitting that in their interrupt handlers, and instead pushing complexity like large or over-aligned stack frames at least a function call away.

https://github.com/llvm/llvm-project/pull/221318