[BPF] override getFrameIndexReference to fix stack offset calculation

llvm/lib/Target/BPF/BPFFrameLowering.cpp

@@ -36,3 +36,18 @@ void BPFFrameLowering::determineCalleeSaves(MachineFunction &MF,
   SavedRegs.reset(BPF::R8);
   SavedRegs.reset(BPF::R9);
 }
+
+StackOffset BPFFrameLowering::getFrameIndexReference(const MachineFunction &MF,
+                                                     int FI,
+                                                     Register &FrameReg) const {
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  const TargetRegisterInfo *RI = MF.getSubtarget().getRegisterInfo();
+
+  FrameReg = RI->getFrameRegister(MF);
+
+  // BPF uses a fixed frame pointer (R10), and offsets are already relative to
+  // it. No StackSize adjustment (as in the default implementation) is needed.
+  return StackOffset::getFixed(MFI.getObjectOffset(FI) -
+                               getOffsetOfLocalArea() +
+                               MFI.getOffsetAdjustment());
+}

llvm/lib/Target/BPF/BPFFrameLowering.h

@@ -35,6 +35,9 @@ class BPFFrameLowering : public TargetFrameLowering {
     return MBB.erase(MI);
   }
 
+  StackOffset getFrameIndexReference(const MachineFunction &MF, int FI,
+                                     Register &FrameReg) const override;
+
 protected:
   bool hasFPImpl(const MachineFunction &MF) const override;
 };