[llvm] [AVR] Add LDS/STS disassemble (PR #146325)

[Tom Vijlbrief via llvm-commits]

https://github.com/tomtor created https://github.com/llvm/llvm-project/pull/146325

LDS/STS instructions are shown as `<unknown>` with `llvm-objdump -d`.

This PR adds the missing decode.

>From 0456f6f4af3af136ec476af61a1192429db42b62 Mon Sep 17 00:00:00 2001
From: Tom Vijlbrief <tvijlbrief at gmail.com>
Date: Mon, 30 Jun 2025 10:05:25 +0200
Subject: [PATCH] Add LDS/STS disassemble

---
 .../AVR/Disassembler/AVRDisassembler.cpp      | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp b/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp
index c7a584868f4e6..d18bdf87ebf17 100644
--- a/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp
+++ b/llvm/lib/Target/AVR/Disassembler/AVRDisassembler.cpp
@@ -433,6 +433,22 @@ static DecodeStatus decodeLoadStore(MCInst &Inst, unsigned Insn,
   return MCDisassembler::Success;
 }
 
+static DecodeStatus decodeLoadStore32(MCInst &Inst, unsigned Insn,
+                                      uint64_t Address,
+                                      const MCDisassembler *Decoder) {
+  // Get the register that will be loaded or stored.
+  unsigned RegVal = GPRDecoderTable[(Insn >> 20) & 0x1f];
+
+  // Decode LDS/STS
+  if ((Insn & 0xfc0f0000) == 0x90000000) {
+    Inst.setOpcode((Insn & 0x02000000) ? AVR::STSKRr : AVR::LDSRdK);
+    Inst.addOperand(MCOperand::createReg(RegVal));
+    Inst.addOperand(MCOperand::createImm(Insn & 0xFFFF));
+    return MCDisassembler::Success;
+  }
+  return MCDisassembler::Fail;
+}
+
 static DecodeStatus readInstruction16(ArrayRef<uint8_t> Bytes, uint64_t Address,
                                       uint64_t &Size, uint32_t &Insn) {
   if (Bytes.size() < 2) {
@@ -523,6 +539,10 @@ DecodeStatus AVRDisassembler::getInstruction(MCInst &Instr, uint64_t &Size,
       return Result;
     }
 
+    Result = decodeLoadStore32(Instr, Insn, Address, this);
+    if (Result != MCDisassembler::Fail)
+      return Result;
+
     return MCDisassembler::Fail;
   }
 }