[llvm] [PATCH] [Xtensa] Implement FrameLowering methods and stack operation lowering. (PR #92960)

[Matt Arsenault via llvm-commits]

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@@ -57,3 +205,31 @@ MachineBasicBlock::iterator XtensaFrameLowering::eliminateCallFramePseudoInstr(
 
   return MBB.erase(I);
 }
+
+void XtensaFrameLowering::determineCalleeSaves(MachineFunction &MF,
+                                               BitVector &SavedRegs,
+                                               RegScavenger *RS) const {
+  MachineFrameInfo &MFI = MF.getFrameInfo();
+  const XtensaRegisterInfo *RegInfo = static_cast<const XtensaRegisterInfo *>(
+      MF.getSubtarget().getRegisterInfo());
+  unsigned FP = RegInfo->getFrameRegister(MF);
+
+  TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
+
+  // Mark $fp as used if function has dedicated frame pointer.
+  if (hasFP(MF))
+    SavedRegs.set(FP);
+
+  // Set scavenging frame index if necessary.
+  uint64_t MaxSPOffset = MFI.estimateStackSize(MF);
+
+  if (isInt<12>(MaxSPOffset))
+    return;
+
+  const TargetRegisterClass &RC = Xtensa::ARRegClass;
+  const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
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arsenm wrote:

Ditto 

https://github.com/llvm/llvm-project/pull/92960