[llvm] [Xtensa] Implement volatile load/store. (PR #110292)

[Matt Arsenault via llvm-commits]

================
@@ -1104,10 +1104,24 @@ XtensaTargetLowering::emitSelectCC(MachineInstr &MI,
 MachineBasicBlock *XtensaTargetLowering::EmitInstrWithCustomInserter(
     MachineInstr &MI, MachineBasicBlock *MBB) const {
   DebugLoc DL = MI.getDebugLoc();
+  const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
 
   switch (MI.getOpcode()) {
   case Xtensa::SELECT:
     return emitSelectCC(MI, MBB);
+  case Xtensa::S8I:
+  case Xtensa::S16I:
+  case Xtensa::S32I:
+  case Xtensa::L8UI:
+  case Xtensa::L16SI:
+  case Xtensa::L16UI:
+  case Xtensa::L32I: {
+    const MachineMemOperand &MMO = **MI.memoperands_begin();
+    if (MMO.isVolatile()) {
----------------
arsenm wrote:

Comment why this is needed? It's also possible memory operands get lost during selection, should defend against missing MMO and assume volatile if it's missing 

https://github.com/llvm/llvm-project/pull/110292