From 1b9a7a48275783e0788eb977cbdaff93a3a282fc Mon Sep 17 00:00:00 2001
From: Lixuanwang <xlwmail@nudt.edu.cn>
Date: Mon, 4 Aug 2025 01:57:34 +0800
Subject: [PATCH] =?UTF-8?q?[backend]=E4=BF=AE=E5=A4=8D=E4=BA=86=E5=87=BD?=
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---
 .../RISCv64/Handler/PrologueEpilogueInsertion.cpp        | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/backend/RISCv64/Handler/PrologueEpilogueInsertion.cpp b/src/backend/RISCv64/Handler/PrologueEpilogueInsertion.cpp
index 0eef863..ab91660 100644
--- a/src/backend/RISCv64/Handler/PrologueEpilogueInsertion.cpp
+++ b/src/backend/RISCv64/Handler/PrologueEpilogueInsertion.cpp
@@ -95,16 +95,17 @@ void PrologueEpilogueInsertionPass::runOnMachineFunction(MachineFunction* mfunc)
         // 4.4. 保存所有使用到的被调用者保存寄存器
         int next_available_offset = -(16 + frame_info.locals_size + frame_info.spill_size);
         for (const auto& reg : frame_info.callee_saved_regs_to_store) {
-            // 采用“先使用，后更新”逻辑
+            // 改为“先更新，后使用”逻辑
+            next_available_offset -= 8; // 先为当前寄存器分配下一个可用槽位
             RVOpcodes store_op = isFPR(reg) ? RVOpcodes::FSD : RVOpcodes::SD;
             auto save_cs_reg = std::make_unique<MachineInstr>(store_op);
             save_cs_reg->addOperand(std::make_unique<RegOperand>(reg));
             save_cs_reg->addOperand(std::make_unique<MemOperand>(
                 std::make_unique<RegOperand>(PhysicalReg::S0),
-                std::make_unique<ImmOperand>(next_available_offset) // 使用当前偏移
+                std::make_unique<ImmOperand>(next_available_offset) // 使用新计算出的正确偏移
             ));
             prologue_instrs.push_back(std::move(save_cs_reg));
-            next_available_offset -= 8; // 为下一个寄存器准备偏移
+            // 不再需要在循环末尾递减
         }
 
         // 4.5. 将所有生成的序言指令一次性插入到函数入口
@@ -121,6 +122,7 @@ void PrologueEpilogueInsertionPass::runOnMachineFunction(MachineFunction* mfunc)
                     // 5.1. 恢复被调用者保存寄存器
                     int next_available_offset_restore = -(16 + frame_info.locals_size + frame_info.spill_size);
                     for (const auto& reg : frame_info.callee_saved_regs_to_store) {
+                        next_available_offset_restore -= 8; // 为下一个寄存器准备偏移
                         RVOpcodes load_op = isFPR(reg) ? RVOpcodes::FLD : RVOpcodes::LD;
                         auto restore_cs_reg = std::make_unique<MachineInstr>(load_op);
                         restore_cs_reg->addOperand(std::make_unique<RegOperand>(reg));
@@ -129,7 +131,6 @@ void PrologueEpilogueInsertionPass::runOnMachineFunction(MachineFunction* mfunc)
                             std::make_unique<ImmOperand>(next_available_offset_restore) // 使用当前偏移
                         ));
                         epilogue_instrs.push_back(std::move(restore_cs_reg));
-                        next_available_offset_restore -= 8; // 为下一个寄存器准备偏移
                     }
 
                     // 5.2. 恢复 ra 和 s0