[llvm] [MC][AsmPrinter] Introduce llvm_reg_offset pseudo cfi instruction. (PR #125104)

[Mikhail Gudim via llvm-commits]

================
@@ -1518,6 +1538,8 @@ void FrameEmitterImpl::emitCFIInstruction(const MCCFIInstruction &Instr) {
     }
     return;
   }
+  case MCCFIInstruction::OpLLVMRegOffset:
+    llvm_unreachable("Should emit llvm_reg_offset as escape");
----------------
mgudim wrote:

> Why don't we emit something to the streamer here?

The sequence of calls is `AsmPrinter::emitFunctionBody()  -> AsmPrinter::emitCFIInstruction(const MachineInstr &MI) ->  AsmPrinter::emitCFIInstruction(const MCCFIInstruction &Inst)`. The last one turns `OpLLVMRegOffset` into escape. By the time we come to `FrameEmitterImpl::emitCFIInstruction(const MCCFIInstruction &Instr)` there should be no `OpLLVMRegOffset`, only `OpEscape`

https://github.com/llvm/llvm-project/pull/125104