[clang] [llvm] [RISCV] SiFive CLIC Support (PR #132481)

[Sam Elliott via llvm-commits]

================
@@ -1502,6 +1659,9 @@ void RISCVFrameLowering::determineCalleeSaves(MachineFunction &MF,
   auto *RVFI = MF.getInfo<RISCVMachineFunctionInfo>();
   if (RVFI->isPushable(MF) && SavedRegs.test(RISCV::X26))
     SavedRegs.set(RISCV::X27);
+
+  // SiFive Preemptible Interrupt Handlers need additional frame entries
+  createSiFivePreemptibleInterruptFrameEntries(MF, *RVFI);
----------------
lenary wrote:

I'm not entirely sure. Those two are used to work out which are conventional callee-saves when sorting the frame objects. If I include the two additional frame objects, it entirely reorders the callee-saves on the stack, which might be ok, but it's hard to tell. The two variables are also used in `computeFreeStackSlots`, which is what enabled #125959 - so it's probably best that we mark these as live as the other callee-saved frame objects.

https://github.com/llvm/llvm-project/pull/132481