[midend-Alias]应用别名分析结果，sccp现在能简单传播数组元素了

src/midend/Pass/Optimize/SCCP.cpp

@@ -1,10 +1,12 @@
 #include "SCCP.h"
 #include "Dom.h"
 #include "Liveness.h"
+#include "SideEffectAnalysis.h"
 #include <algorithm>
 #include <cassert>
 #include <cmath>  // For std::fmod, std::fabs
 #include <limits> // For std::numeric_limits
+#include <set>    // For std::set in isKnownPureFunction
 
 namespace sysy {
 
@@ -263,6 +265,192 @@ SSAPValue SCCPContext::ComputeConstant(UnaryInst *unaryInst, SSAPValue operandVa
   return SSAPValue(LatticeVal::Bottom);
 }
 
+// 辅助函数：检查是否为已知的纯函数
+bool SCCPContext::isKnownPureFunction(const std::string &funcName) const {
+  // SysY中一些已知的纯函数（不修改全局状态，结果只依赖参数）
+  static const std::set<std::string> knownPureFunctions = {
+    // 数学函数（如果有的话）
+    // "abs", "fabs", "sqrt", "sin", "cos"
+    // SysY标准中基本没有纯函数，大多数都有I/O副作用
+  };
+  
+  return knownPureFunctions.find(funcName) != knownPureFunctions.end();
+}
+
+// 辅助函数：计算纯函数的常量结果
+SSAPValue SCCPContext::computePureFunctionResult(CallInst *call, const std::vector<SSAPValue> &argValues) {
+  Function *calledFunc = call->getCallee();
+  if (!calledFunc) {
+    return SSAPValue(LatticeVal::Bottom);
+  }
+  
+  std::string funcName = calledFunc->getName();
+  
+  // 目前SysY中没有标准的纯函数，这里预留扩展空间
+  // 未来可以添加数学函数的常量折叠
+  /*
+  if (funcName == "abs" && argValues.size() == 1) {
+    if (argValues[0].constant_type == ValueType::Integer) {
+      int val = std::get<int>(argValues[0].constantVal);
+      return SSAPValue(std::abs(val));
+    }
+  }
+  */
+  
+  return SSAPValue(LatticeVal::Bottom);
+}
+
+// 辅助函数：查找存储到指定位置的常量值
+SSAPValue SCCPContext::findStoredConstantValue(Value *ptr, BasicBlock *currentBB) {
+  if (!aliasAnalysis) {
+    if (DEBUG) {
+      std::cout << "SCCP: No alias analysis available" << std::endl;
+    }
+    return SSAPValue(LatticeVal::Bottom);
+  }
+  
+  if (DEBUG) {
+    std::cout << "SCCP: Searching for stored constant value for ptr" << std::endl;
+  }
+  
+  // 从当前块的指令列表末尾向前查找最近的Store
+  std::vector<Instruction*> instructions;
+  for (auto it = currentBB->begin(); it != currentBB->end(); ++it) {
+    instructions.push_back(it->get());
+  }
+  
+  for (int i = instructions.size() - 1; i >= 0; --i) {
+    Instruction *prevInst = instructions[i];
+    
+    if (prevInst->isStore()) {
+      StoreInst *storeInst = static_cast<StoreInst *>(prevInst);
+      Value *storePtr = storeInst->getPointer();
+      
+      if (DEBUG) {
+        std::cout << "SCCP: Checking store instruction" << std::endl;
+      }
+      
+      // 使用别名分析检查Store是否针对相同的内存位置
+      auto aliasResult = aliasAnalysis->queryAlias(ptr, storePtr);
+      
+      if (DEBUG) {
+        std::cout << "SCCP: Alias result: " << (int)aliasResult << std::endl;
+      }
+      
+      if (aliasResult == AliasType::SELF_ALIAS) {
+        // 找到了对相同位置的Store，获取存储的值
+        Value *storedValue = storeInst->getValue();
+        
+        if (DEBUG) {
+          std::cout << "SCCP: Found matching store, checking value type" << std::endl;
+        }
+        
+        // 检查存储的值是否为常量
+        if (auto constInt = dynamic_cast<ConstantInteger *>(storedValue)) {
+          int val = std::get<int>(constInt->getVal());
+          if (DEBUG) {
+            std::cout << "SCCP: Found constant integer value: " << val << std::endl;
+          }
+          return SSAPValue(val);
+        } else if (auto constFloat = dynamic_cast<ConstantFloating *>(storedValue)) {
+          float val = std::get<float>(constFloat->getVal());
+          if (DEBUG) {
+            std::cout << "SCCP: Found constant float value: " << val << std::endl;
+          }
+          return SSAPValue(val);
+        } else {
+          // 存储的值不是常量，检查其SCCP状态
+          SSAPValue storedState = GetValueState(storedValue);
+          if (storedState.state == LatticeVal::Constant) {
+            if (DEBUG) {
+              std::cout << "SCCP: Found SCCP constant value" << std::endl;
+            }
+            return storedState;
+          } else {
+            if (DEBUG) {
+              std::cout << "SCCP: Stored value is not constant" << std::endl;
+            }
+          }
+        }
+        
+        // 找到了最近的Store但不是常量，停止查找
+        if (DEBUG) {
+          std::cout << "SCCP: Found non-constant store, stopping search" << std::endl;
+        }
+        break;
+      }
+    }
+  }
+  
+  if (DEBUG) {
+    std::cout << "SCCP: No constant value found" << std::endl;
+  }
+  return SSAPValue(LatticeVal::Bottom);
+}
+
+// 辅助函数：动态检查数组访问是否为常量索引（考虑SCCP状态）
+bool SCCPContext::hasRuntimeConstantAccess(Value *ptr) {
+  if (auto gep = dynamic_cast<GetElementPtrInst *>(ptr)) {
+    if (DEBUG) {
+      std::cout << "SCCP: Checking runtime constant access for GEP instruction" << std::endl;
+    }
+    
+    // 检查所有索引是否为常量或SCCP传播的常量
+    bool allConstantIndices = true;
+    for (auto indexUse : gep->getIndices()) {
+      Value* index = indexUse->getValue();
+      
+      // 首先检查是否为编译时常量
+      if (auto constInt = dynamic_cast<ConstantInteger *>(index)) {
+        if (DEBUG) {
+          std::cout << "SCCP: Index is compile-time constant integer: " << std::get<int>(constInt->getVal()) << std::endl;
+        }
+        continue;
+      }
+      if (auto constFloat = dynamic_cast<ConstantFloating *>(index)) {
+        if (DEBUG) {
+          std::cout << "SCCP: Index is compile-time constant float: " << std::get<float>(constFloat->getVal()) << std::endl;
+        }
+        continue;
+      }
+      
+      // 检查是否为SCCP传播的常量
+      SSAPValue indexState = GetValueState(index);
+      if (indexState.state == LatticeVal::Constant) {
+        if (DEBUG) {
+          std::cout << "SCCP: Index is SCCP constant: ";
+          if (indexState.constant_type == ValueType::Integer) {
+            std::cout << std::get<int>(indexState.constantVal);
+          } else {
+            std::cout << std::get<float>(indexState.constantVal);
+          }
+          std::cout << std::endl;
+        }
+        continue;
+      }
+      
+      // 如果任何一个索引不是常量，返回false
+      if (DEBUG) {
+        std::cout << "SCCP: Index is not constant, access is not constant" << std::endl;
+      }
+      allConstantIndices = false;
+      break;
+    }
+    
+    if (DEBUG) {
+      std::cout << "SCCP: hasRuntimeConstantAccess result: " << (allConstantIndices ? "true" : "false") << std::endl;
+    }
+    return allConstantIndices;
+  }
+  
+  // 对于非GEP指令，回退到别名分析的静态结果
+  if (aliasAnalysis) {
+    return aliasAnalysis->hasConstantAccess(ptr);
+  }
+  
+  return false;
+}
+
 // 辅助函数：处理单条指令
 void SCCPContext::ProcessInstruction(Instruction *inst) {
   SSAPValue oldState = GetValueState(inst);
@@ -380,27 +568,237 @@ void SCCPContext::ProcessInstruction(Instruction *inst) {
     break;
   }
   case Instruction::kLoad: {
-    // 对于 Load 指令，除非我们有特殊的别名分析，否则假定为 Bottom
-    // 或者如果它加载的是一个已知常量地址的全局常量
+    // 使用别名分析和副作用分析改进Load指令的处理
     Value *ptr = inst->getOperand(0);
+    
+    // 首先检查是否是全局常量
     if (auto globalVal = dynamic_cast<GlobalValue *>(ptr)) {
       // 如果 GlobalValue 有初始化器，并且它是常量，我们可以传播
-      // 这需要额外的逻辑来检查 globalVal 的初始化器
-      // 暂时保守地设置为 Bottom
+      // TODO: 检查全局变量的初始化器进行常量传播
       newState = SSAPValue(LatticeVal::Bottom);
+    } else if (aliasAnalysis && sideEffectAnalysis) {
+      // 使用别名分析和副作用分析进行更精确的Load分析
+      if (aliasAnalysis->isLocalArray(ptr) && (aliasAnalysis->hasConstantAccess(ptr) || hasRuntimeConstantAccess(ptr))) {
+        // 对于局部数组的常量索引访问，检查是否有影响该位置的Store
+        bool mayBeModified = false;
+        
+        if (DEBUG) {
+          std::cout << "SCCP: Analyzing local array with constant access for modification" << std::endl;
+        }
+        
+        // 遍历指令所在块之前的所有指令，查找可能修改该内存位置的Store
+        BasicBlock *currentBB = inst->getParent();
+        auto instPos = currentBB->findInstIterator(inst);
+        
+        SSAPValue foundConstantValue = SSAPValue(LatticeVal::Bottom);
+        bool hasFoundDefinitiveStore = false;
+        
+        for (auto it = currentBB->begin(); it != instPos; ++it) {
+          Instruction *prevInst = it->get();
+          
+          if (prevInst->isStore()) {
+            StoreInst *storeInst = static_cast<StoreInst *>(prevInst);
+            Value *storePtr = storeInst->getPointer();
+            
+            // 使用别名分析判断Store是否可能影响当前Load
+            auto aliasResult = aliasAnalysis->queryAlias(ptr, storePtr);
+            if (DEBUG) {
+              std::cout << "SCCP: Checking store with alias result: " << (int)aliasResult << std::endl;
+            }
+            
+            if (aliasResult == AliasType::SELF_ALIAS) {
+              // 找到对相同位置的精确Store
+              Value *storedValue = storeInst->getValue();
+              
+              if (DEBUG) {
+                std::cout << "SCCP: Found exact store to same location, checking value" << std::endl;
+              }
+              
+              // 检查存储的值是否为常量
+              if (auto constInt = dynamic_cast<ConstantInteger *>(storedValue)) {
+                int val = std::get<int>(constInt->getVal());
+                if (DEBUG) {
+                  std::cout << "SCCP: Store contains constant integer: " << val << std::endl;
+                }
+                foundConstantValue = SSAPValue(val);
+                hasFoundDefinitiveStore = true;
+                // 继续遍历，查找是否有更后面的Store覆盖这个值
+              } else if (auto constFloat = dynamic_cast<ConstantFloating *>(storedValue)) {
+                float val = std::get<float>(constFloat->getVal());
+                if (DEBUG) {
+                  std::cout << "SCCP: Store contains constant float: " << val << std::endl;
+                }
+                foundConstantValue = SSAPValue(val);
+                hasFoundDefinitiveStore = true;
+              } else {
+                // 存储的值不是编译时常量，检查其SCCP状态
+                SSAPValue storedState = GetValueState(storedValue);
+                if (storedState.state == LatticeVal::Constant) {
+                  if (DEBUG) {
+                    std::cout << "SCCP: Store contains SCCP constant" << std::endl;
+                  }
+                  foundConstantValue = storedState;
+                  hasFoundDefinitiveStore = true;
+                } else {
+                  if (DEBUG) {
+                    std::cout << "SCCP: Store contains non-constant value" << std::endl;
+                  }
+                  // 非常量Store覆盖了之前的常量，无法传播
+                  foundConstantValue = SSAPValue(LatticeVal::Bottom);
+                  hasFoundDefinitiveStore = true;
+                }
+              }
+            } else if (aliasResult != AliasType::NO_ALIAS) {
+              // 可能有别名，但不确定
+              if (DEBUG) {
+                std::cout << "SCCP: Found store with uncertain alias, stopping propagation" << std::endl;
+              }
+              mayBeModified = true;
+              break;
+            }
+          } else if (prevInst->isCall()) {
+            // 检查函数调用是否可能修改该内存位置
+            if (sideEffectAnalysis->mayModifyMemory(prevInst)) {
+              // 进一步检查是否可能影响局部数组
+              if (!aliasAnalysis->isLocalArray(ptr) || 
+                  sideEffectAnalysis->mayModifyGlobal(prevInst)) {
+                mayBeModified = true;
+                break;
+              }
+            }
+          } else if (prevInst->isMemset()) {
+            // Memset指令可能影响内存，但只有在它在相关Store之前时才阻止常量传播
+            MemsetInst *memsetInst = static_cast<MemsetInst *>(prevInst);
+            Value *memsetPtr = memsetInst->getOperand(0);
+            
+            auto aliasResult = aliasAnalysis->queryAlias(ptr, memsetPtr);
+            if (aliasResult != AliasType::NO_ALIAS) {
+              // Memset可能影响这个位置，但我们继续查找是否有Store覆盖了memset
+              // 不立即设置mayBeModified = true，让后续的Store有机会覆盖
+              if (DEBUG) {
+                std::cout << "SCCP: Found memset that may affect location, but continuing to check for overwriting stores" << std::endl;
+              }
+            }
+          }
+        }
+        
+        if (DEBUG) {
+          std::cout << "SCCP: mayBeModified = " << (mayBeModified ? "true" : "false") << std::endl;
+          std::cout << "SCCP: hasFoundDefinitiveStore = " << (hasFoundDefinitiveStore ? "true" : "false") << std::endl;
+        }
+        
+        if (!mayBeModified) {
+          if (hasFoundDefinitiveStore && foundConstantValue.state == LatticeVal::Constant) {
+            // 直接使用找到的常量值
+            if (DEBUG) {
+              std::cout << "SCCP: Using found constant value from store analysis: ";
+              if (foundConstantValue.constant_type == ValueType::Integer) {
+                std::cout << std::get<int>(foundConstantValue.constantVal);
+              } else {
+                std::cout << std::get<float>(foundConstantValue.constantVal);
+              }
+              std::cout << std::endl;
+            }
+            newState = foundConstantValue;
+          } else {
+            // 如果没有发现修改该位置的指令，尝试用旧方法找到对应的Store值
+            SSAPValue constantValue = findStoredConstantValue(ptr, inst->getParent());
+            if (constantValue.state == LatticeVal::Constant) {
+              if (DEBUG) {
+                std::cout << "SCCP: Found constant value for array load using fallback method: ";
+                if (constantValue.constant_type == ValueType::Integer) {
+                  std::cout << std::get<int>(constantValue.constantVal);
+                } else {
+                  std::cout << std::get<float>(constantValue.constantVal);
+                }
+                std::cout << std::endl;
+              }
+              newState = constantValue;
+            } else {
+              newState = SSAPValue(LatticeVal::Bottom);
+            }
+          }
+        } else {
+          newState = SSAPValue(LatticeVal::Bottom);
+        }
+      } else {
+        // 非局部数组或非常量访问，保守处理
+        newState = SSAPValue(LatticeVal::Bottom);
+      }
     } else {
+      // 没有分析信息时保守处理
       newState = SSAPValue(LatticeVal::Bottom);
     }
+    
+    if (DEBUG && aliasAnalysis && sideEffectAnalysis) {
+      std::cout << "SCCP: Load instruction analysis - " 
+                << (aliasAnalysis->isLocalArray(ptr) ? "local array" : "other")
+                << ", static constant access: " 
+                << (aliasAnalysis->hasConstantAccess(ptr) ? "yes" : "no")
+                << ", runtime constant access: "
+                << (hasRuntimeConstantAccess(ptr) ? "yes" : "no") << std::endl;
+    }
     break;
   }
   case Instruction::kStore:
     // Store 指令不产生值，其 SSAPValue 不重要
     newState = SSAPValue(); // 保持 Top
     break;
-  case Instruction::kCall:
-    // 大多数 Call 指令都假定为 Bottom，除非是纯函数且所有参数都是常量
-    newState = SSAPValue(LatticeVal::Bottom);
+  case Instruction::kCall: {
+    // 使用副作用分析改进Call指令处理
+    CallInst *callInst = static_cast<CallInst *>(inst);
+    
+    if (sideEffectAnalysis) {
+      const auto &sideEffect = sideEffectAnalysis->getInstructionSideEffect(callInst);
+      
+      // 检查是否为纯函数且所有参数都是常量
+      if (sideEffect.isPure && sideEffect.type == SideEffectType::NO_SIDE_EFFECT) {
+        // 对于纯函数，检查所有参数是否都是常量
+        bool allArgsConstant = true;
+        std::vector<SSAPValue> argValues;
+        
+        for (unsigned i = 0; i < callInst->getNumOperands() - 1; ++i) { // 减1排除函数本身
+          SSAPValue argVal = GetValueState(callInst->getOperand(i));
+          argValues.push_back(argVal);
+          if (argVal.state != LatticeVal::Constant) {
+            allArgsConstant = false;
+            break;
+          }
+        }
+        
+        if (allArgsConstant) {
+          // 对于参数全为常量的纯函数，可以尝试常量折叠
+          // 但由于实际执行函数比较复杂，这里先标记为可优化
+          // TODO: 实现具体的纯函数常量折叠
+          Function *calledFunc = callInst->getCallee();
+          if (calledFunc && isKnownPureFunction(calledFunc->getName())) {
+            // 对已知的纯函数进行常量计算
+            newState = computePureFunctionResult(callInst, argValues);
+          } else {
+            newState = SSAPValue(LatticeVal::Bottom);
+          }
+        } else {
+          // 参数不全是常量，但函数无副作用
+          newState = SSAPValue(LatticeVal::Bottom);
+        }
+        
+        if (DEBUG) {
+          std::cout << "SCCP: Pure function call with " 
+                    << (allArgsConstant ? "constant" : "non-constant") << " arguments" << std::endl;
+        }
+      } else {
+        // 有副作用的函数调用，保守处理
+        newState = SSAPValue(LatticeVal::Bottom);
+        if (DEBUG) {
+          std::cout << "SCCP: Function call with side effects" << std::endl;
+        }
+      }
+    } else {
+      // 没有副作用分析时，保守处理所有Call
+      newState = SSAPValue(LatticeVal::Bottom);
+    }
     break;
+  }
   case Instruction::kGetElementPtr: {
     // GEP 指令计算地址，通常其结果值（地址指向的内容）是 Bottom
     // 除非所有索引和基指针都是常量，指向一个确定常量值的内存位置
@@ -866,12 +1264,34 @@ bool SCCP::runOnFunction(Function *F, AnalysisManager &AM) {
   if (DEBUG) {
     std::cout << "Running SCCP on function: " << F->getName() << std::endl;
   }
+  
   SCCPContext context(builder);
+  
+  // 获取别名分析结果
+  if (auto *aliasResult = AM.getAnalysisResult<AliasAnalysisResult, SysYAliasAnalysisPass>(F)) {
+    context.setAliasAnalysis(aliasResult);
+    if (DEBUG) {
+      std::cout << "SCCP: Using alias analysis results" << std::endl;
+    }
+  }
+  
+  // 获取副作用分析结果
+  if (auto *sideEffectResult = AM.getAnalysisResult<SideEffectAnalysisResult, SysYSideEffectAnalysisPass>(F)) {
+    context.setSideEffectAnalysis(sideEffectResult);
+    if (DEBUG) {
+      std::cout << "SCCP: Using side effect analysis results" << std::endl;
+    }
+  }
+  
   context.run(F, AM);
   return true;
 }
 
 void SCCP::getAnalysisUsage(std::set<void *> &analysisDependencies, std::set<void *> &analysisInvalidations) const {
+  // 声明依赖别名分析和副作用分析
+  analysisDependencies.insert(&SysYAliasAnalysisPass::ID);
+  analysisDependencies.insert(&SysYSideEffectAnalysisPass::ID);
+  
   // analysisInvalidations.insert(nullptr); // 表示使所有默认分析失效
   analysisInvalidations.insert(&DominatorTreeAnalysisPass::ID); // 支配树可能受影响
   analysisInvalidations.insert(&LivenessAnalysisPass::ID); // 活跃性分析很可能失效