From 3ef7bc28d67a6190a14a7bb9b3c0e0a5fabb3f7a Mon Sep 17 00:00:00 2001
From: CGH0S7 <776459475@qq.com>
Date: Tue, 30 Jun 2026 00:48:57 +0800
Subject: [PATCH] lower integer add-sub with immediates

---
 src/mir/Lowering.cpp | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/src/mir/Lowering.cpp b/src/mir/Lowering.cpp
index 1b69997..f844d95 100644
--- a/src/mir/Lowering.cpp
+++ b/src/mir/Lowering.cpp
@@ -368,6 +368,34 @@ void LowerInstruction(const ir::Instruction& inst, MachineFunction& function,
       int dst_slot = function.CreateFrameIndex(4);
       slots.emplace(&inst, dst_slot);
 
+      if (inst.GetOpcode() == ir::Opcode::Add) {
+        const ir::Value* variable = nullptr;
+        int constant = 0;
+        if (auto* lhs_const = dynamic_cast<const ir::ConstantInt*>(bin.GetLhs())) {
+          variable = bin.GetRhs();
+          constant = lhs_const->GetValue();
+        } else if (auto* rhs_const = dynamic_cast<const ir::ConstantInt*>(bin.GetRhs())) {
+          variable = bin.GetLhs();
+          constant = rhs_const->GetValue();
+        }
+        if (variable && constant >= -4095 && constant <= 4095) {
+          EmitValueToReg(variable, PhysReg::W8, slots, block);
+          block.Append(Opcode::AddRegImm, {Operand::Reg(PhysReg::W8), Operand::Reg(PhysReg::W8), Operand::Imm(constant)});
+          block.Append(Opcode::StoreStack, {Operand::Reg(PhysReg::W8), Operand::FrameIndex(dst_slot)});
+          return;
+        }
+      } else if (inst.GetOpcode() == ir::Opcode::Sub) {
+        if (auto* rhs_const = dynamic_cast<const ir::ConstantInt*>(bin.GetRhs())) {
+          int constant = rhs_const->GetValue();
+          if (constant >= -4095 && constant <= 4095) {
+            EmitValueToReg(bin.GetLhs(), PhysReg::W8, slots, block);
+            block.Append(Opcode::AddRegImm, {Operand::Reg(PhysReg::W8), Operand::Reg(PhysReg::W8), Operand::Imm(-constant)});
+            block.Append(Opcode::StoreStack, {Operand::Reg(PhysReg::W8), Operand::FrameIndex(dst_slot)});
+            return;
+          }
+        }
+      }
+
       if (inst.GetOpcode() == ir::Opcode::Mul) {
         const ir::Value* variable = nullptr;
         int constant = 0;