From c4eb1c39808730d2fd5034e0540a37bef0712de0 Mon Sep 17 00:00:00 2001
From: rain2133 <1370973498@qq.com>
Date: Sat, 16 Aug 2025 18:52:29 +0800
Subject: [PATCH] =?UTF-8?q?[midend-GVN&SideEffect]=E4=BF=AE=E5=A4=8DGVN?=
 =?UTF-8?q?=E7=9A=84=E9=83=A8=E5=88=86=E9=97=AE=E9=A2=98=E5=92=8C=E5=89=AF?=
 =?UTF-8?q?=E4=BD=9C=E7=94=A8=E5=88=86=E6=9E=90=E7=9A=84=E7=BC=BA=E9=99=B7?=
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---
 src/include/midend/Pass/Optimize/GVN.h        |  3 +
 .../Pass/Analysis/SideEffectAnalysis.cpp      | 11 +++
 src/midend/Pass/Optimize/GVN.cpp              | 75 +++++++++++++++++--
 3 files changed, 83 insertions(+), 6 deletions(-)

diff --git a/src/include/midend/Pass/Optimize/GVN.h b/src/include/midend/Pass/Optimize/GVN.h
index 3358e48..ce11769 100644
--- a/src/include/midend/Pass/Optimize/GVN.h
+++ b/src/include/midend/Pass/Optimize/GVN.h
@@ -56,6 +56,9 @@ private:
     // 检查是否可以安全地用一个值替换另一个值
     bool canReplace(Instruction* original, Value* replacement);
     
+    // 检查两个load指令之间是否有store指令修改了相同的内存位置
+    bool hasInterveningStore(LoadInst* earlierLoad, LoadInst* laterLoad, Value* ptr);
+    
     // 生成表达式的标准化字符串
     std::string getCanonicalExpression(Instruction* inst);
 };
diff --git a/src/midend/Pass/Analysis/SideEffectAnalysis.cpp b/src/midend/Pass/Analysis/SideEffectAnalysis.cpp
index 805f98b..3887add 100644
--- a/src/midend/Pass/Analysis/SideEffectAnalysis.cpp
+++ b/src/midend/Pass/Analysis/SideEffectAnalysis.cpp
@@ -26,10 +26,21 @@ const SideEffectInfo &SideEffectAnalysisResult::getInstructionSideEffect(Instruc
 }
 
 const SideEffectInfo &SideEffectAnalysisResult::getFunctionSideEffect(Function *func) const {
+  // 首先检查分析过的用户定义函数
   auto it = functionSideEffects.find(func);
   if (it != functionSideEffects.end()) {
     return it->second;
   }
+  
+  // 如果没有找到，检查是否为已知的库函数
+  if (func) {
+    std::string funcName = func->getName();
+    const SideEffectInfo *knownInfo = getKnownFunctionSideEffect(funcName);
+    if (knownInfo) {
+      return *knownInfo;
+    }
+  }
+  
   // 返回默认的无副作用信息
   static SideEffectInfo noEffect;
   return noEffect;
diff --git a/src/midend/Pass/Optimize/GVN.cpp b/src/midend/Pass/Optimize/GVN.cpp
index a06ec5f..76b0ffb 100644
--- a/src/midend/Pass/Optimize/GVN.cpp
+++ b/src/midend/Pass/Optimize/GVN.cpp
@@ -201,7 +201,11 @@ Value *GVNContext::getValueNumber(Instruction *inst) {
   } else if (auto load = dynamic_cast<LoadInst *>(inst)) {
     return getValueNumber(load);
   } else if (auto call = dynamic_cast<CallInst *>(inst)) {
-    return getValueNumber(call);
+    // 只为无副作用的函数调用进行GVN
+    if (sideEffectAnalysis && sideEffectAnalysis->isPureFunction(call->getCallee())) {
+      return getValueNumber(call);
+    }
+    return nullptr;
   }
 
   return nullptr;
@@ -295,6 +299,10 @@ Value *GVNContext::getValueNumber(LoadInst *inst) {
       auto loadPtr = checkHashtable(load->getPointer());
 
       if (ptr == loadPtr && inst->getType() == load->getType()) {
+        // 检查两次load之间是否有store指令修改了内存
+        if (hasInterveningStore(load, inst, ptr)) {
+          continue; // 如果有store指令，不能复用之前的load
+        }
         return value;
       }
     }
@@ -304,11 +312,7 @@ Value *GVNContext::getValueNumber(LoadInst *inst) {
 }
 
 Value *GVNContext::getValueNumber(CallInst *inst) {
-  // 只为无副作用的函数调用进行GVN
-  if (sideEffectAnalysis && !sideEffectAnalysis->isPureFunction(inst->getCallee())) {
-    return nullptr;
-  }
-
+  // 此时已经确认是无副作用的函数调用，可以安全进行GVN
   for (auto [key, value] : hashtable) {
     if (auto call = dynamic_cast<CallInst *>(key)) {
       if (call->getCallee() == inst->getCallee() && call->getNumOperands() == inst->getNumOperands()) {
@@ -427,6 +431,65 @@ bool GVNContext::canReplace(Instruction *original, Value *replacement) {
   return false;
 }
 
+bool GVNContext::hasInterveningStore(LoadInst* earlierLoad, LoadInst* laterLoad, Value* ptr) {
+  // 如果两个load在不同的基本块，需要更复杂的分析
+  auto earlierBB = earlierLoad->getParent();
+  auto laterBB = laterLoad->getParent();
+  
+  if (earlierBB != laterBB) {
+    // 跨基本块的情况：为了安全起见，暂时认为有intervening store
+    // 这是保守的做法，可能会错过一些优化机会，但确保正确性
+    return true;
+  }
+  
+  // 同一基本块内的情况：检查指令序列
+  auto &insts = earlierBB->getInstructions();
+  
+  // 找到两个load指令的位置
+  auto earlierIt = std::find_if(insts.begin(), insts.end(), 
+                               [earlierLoad](const auto &ptr) { return ptr.get() == earlierLoad; });
+  auto laterIt = std::find_if(insts.begin(), insts.end(),
+                              [laterLoad](const auto &ptr) { return ptr.get() == laterLoad; });
+  
+  if (earlierIt == insts.end() || laterIt == insts.end()) {
+    return true; // 找不到指令，保守返回true
+  }
+  
+  // 检查两个load之间的所有指令
+  for (auto it = std::next(earlierIt); it != laterIt; ++it) {
+    auto inst = it->get();
+    
+    // 检查是否是store指令
+    if (auto storeInst = dynamic_cast<StoreInst*>(inst)) {
+      auto storePtr = checkHashtable(storeInst->getPointer());
+      
+      // 如果store的目标地址与load的地址相同，说明内存被修改了
+      if (storePtr == ptr) {
+        if (DEBUG) {
+          std::cout << "          Found intervening store to same address, cannot optimize load" << std::endl;
+        }
+        return true;
+      }
+    }
+    
+    // TODO: 还需要检查函数调用是否可能修改内存
+    // 对于全局变量，任何函数调用都可能修改它
+    if (auto callInst = dynamic_cast<CallInst*>(inst)) {
+      if (sideEffectAnalysis && !sideEffectAnalysis->isPureFunction(callInst->getCallee())) {
+        // 如果是有副作用的函数调用，且load的是全局变量，则可能被修改
+        if (auto globalPtr = dynamic_cast<GlobalValue*>(ptr)) {
+          if (DEBUG) {
+            std::cout << "          Found function call that may modify global variable, cannot optimize load" << std::endl;
+          }
+          return true;
+        }
+      }
+    }
+  }
+  
+  return false; // 没有找到会修改内存的指令
+}
+
 std::string GVNContext::getCanonicalExpression(Instruction *inst) {
   std::ostringstream oss;