From f292d53c70f96ca2beee448fb9bf2debaf0134a0 Mon Sep 17 00:00:00 2001
From: wanglei <wanglei@loongson.cn>
Date: Wed, 11 Jan 2023 21:16:38 +0800
Subject: [PATCH] [LoongArch] Fix undefined behavior: left shift of negative
 value

Fix undefined behavior in `decodeSImmOperand` where we were left shifting
a signed value.
---
 llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp b/llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp
index beb757c..2335152 100644
--- a/llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp
+++ b/llvm/lib/Target/LoongArch/Disassembler/LoongArchDisassembler.cpp
@@ -114,9 +114,9 @@ static DecodeStatus decodeSImmOperand(MCInst &Inst, uint64_t Imm,
                                       int64_t Address,
                                       const MCDisassembler *Decoder) {
   assert(isUInt<N>(Imm) && "Invalid immediate");
-  // Sign-extend the number in the bottom <N> bits of Imm, then shift left <S>
+  // Shift left Imm <S> bits, then sign-extend the number in the bottom <N+S>
   // bits.
-  Inst.addOperand(MCOperand::createImm(SignExtend64<N>(Imm) << S));
+  Inst.addOperand(MCOperand::createImm(SignExtend64<N + S>(Imm << S)));
   return MCDisassembler::Success;
 }
 
-- 
2.7.4