[midend-GSR]将魔数求解移动到utils的静态方法中。

src/include/midend/Pass/Optimize/GlobalStrengthReduction.h

@@ -68,7 +68,7 @@ private:
     MagicNumber computeMagicNumber(uint32_t divisor);
     std::pair<int, int> computeMulhMagicNumbers(int divisor);
     Value* createMagicDivision(BinaryInst* divInst, uint32_t divisor, const MagicNumber& magic);
-    Value* createMagicDivisionLibdivide(BinaryInst* divInst, int divisor, const std::pair<int, int>& magicPair);
+    Value* createMagicDivisionLibdivide(BinaryInst* divInst, int divisor);
     bool isPowerOfTwo(uint32_t n);
     int log2OfPowerOfTwo(uint32_t n);
     

src/include/midend/Pass/Optimize/LoopStrengthReduction.h

@@ -127,13 +127,6 @@ private:
    */
   bool analyzeInductionVariableRange(const InductionVarInfo* ivInfo, Loop* loop) const;
   
-  /**
-   * 计算用于除法优化的魔数和移位量
-   * @param divisor 除数
-   * @return {魔数, 移位量}
-   */
-  std::pair<int, int> computeMulhMagicNumbers(int divisor) const;
-  
   /**
    * 生成除法替换代码
    * @param candidate 优化候选项

src/include/midend/Pass/Optimize/SysYIROptUtils.h

@@ -107,6 +107,190 @@ public:
     // 所以当AllocaInst的basetype是PointerType时（一维数组）或者是指向ArrayType的PointerType（多位数组）时，返回true
     return aval && (baseType->isPointer() || baseType->as<PointerType>()->getBaseType()->isArray());
   }
+
+  
+  //该实现参考了libdivide的算法
+  static std::pair<int, int> computeMulhMagicNumbers(int divisor) {
+    
+    if (DEBUG) {
+      std::cout << "\n[SR] ===== Computing magic numbers for divisor " << divisor << " (libdivide algorithm) =====" << std::endl;
+    }
+    
+    if (divisor == 0) {
+      if (DEBUG) std::cout << "[SR] Error: divisor must be != 0" << std::endl;
+      return {-1, -1};
+    }
+
+    // libdivide 常数
+    const uint8_t LIBDIVIDE_ADD_MARKER = 0x40;
+    const uint8_t LIBDIVIDE_NEGATIVE_DIVISOR = 0x80;
+    
+    // 辅助函数：计算前导零个数
+    auto count_leading_zeros32 = [](uint32_t val) -> uint32_t {
+      if (val == 0) return 32;
+      return __builtin_clz(val);
+    };
+    
+    // 辅助函数：64位除法返回32位商和余数
+    auto div_64_32 = [](uint32_t high, uint32_t low, uint32_t divisor, uint32_t* rem) -> uint32_t {
+      uint64_t dividend = ((uint64_t)high << 32) | low;
+      uint32_t quotient = dividend / divisor;
+      *rem = dividend % divisor;
+      return quotient;
+    };
+
+    if (DEBUG) {
+      std::cout << "[SR] Input divisor: " << divisor << std::endl;
+    }
+
+    // libdivide_internal_s32_gen 算法实现
+    int32_t d = divisor;
+    uint32_t ud = (uint32_t)d;
+    uint32_t absD = (d < 0) ? -ud : ud;
+    
+    if (DEBUG) {
+      std::cout << "[SR] absD = " << absD << std::endl;
+    }
+    
+    uint32_t floor_log_2_d = 31 - count_leading_zeros32(absD);
+    
+    if (DEBUG) {
+      std::cout << "[SR] floor_log_2_d = " << floor_log_2_d << std::endl;
+    }
+    
+    // 检查 absD 是否为2的幂
+    if ((absD & (absD - 1)) == 0) {
+      if (DEBUG) {
+        std::cout << "[SR] " << absD << " 是2的幂，使用移位方法" << std::endl;
+      }
+      
+      // 对于2的幂，我们只使用移位，不需要魔数
+      int shift = floor_log_2_d;
+      if (d < 0) shift |= 0x80; // 标记负数
+      
+      if (DEBUG) {
+        std::cout << "[SR] Power of 2 result: magic=0, shift=" << shift << std::endl;
+        std::cout << "[SR] ===== End magic computation =====" << std::endl;
+      }
+      
+      // 对于我们的目的，我们将在IR生成中以不同方式处理2的幂
+      // 返回特殊标记
+      return {0, shift};
+    }
+    
+    if (DEBUG) {
+      std::cout << "[SR] " << absD << " is not a power of 2, computing magic number" << std::endl;
+    }
+    
+    // 非2的幂除数的魔数计算
+    uint8_t more;
+    uint32_t rem, proposed_m;
+    
+    // 计算 proposed_m = floor(2^(floor_log_2_d + 31) / absD)
+    proposed_m = div_64_32((uint32_t)1 << (floor_log_2_d - 1), 0, absD, &rem);
+    const uint32_t e = absD - rem;
+    
+    if (DEBUG) {
+      std::cout << "[SR] proposed_m = " << proposed_m << ", rem = " << rem << ", e = " << e << std::endl;
+    }
+    
+    // 确定是否需要"加法"版本
+    const bool branchfree = false; // 使用分支版本
+    
+    if (!branchfree && e < ((uint32_t)1 << floor_log_2_d)) {
+      // 这个幂次有效
+      more = (uint8_t)(floor_log_2_d - 1);
+      if (DEBUG) {
+        std::cout << "[SR] Using basic algorithm, shift = " << (int)more << std::endl;
+      }
+    } else {
+      // 我们需要上升一个等级
+      proposed_m += proposed_m;
+      const uint32_t twice_rem = rem + rem;
+      if (twice_rem >= absD || twice_rem < rem) {
+        proposed_m += 1;
+      }
+      more = (uint8_t)(floor_log_2_d | LIBDIVIDE_ADD_MARKER);
+      if (DEBUG) {
+        std::cout << "[SR] Using add algorithm, proposed_m = " << proposed_m << ", more = " << (int)more << std::endl;
+      }
+    }
+    
+    proposed_m += 1;
+    int32_t magic = (int32_t)proposed_m;
+    
+    // 处理负除数
+    if (d < 0) {
+      more |= LIBDIVIDE_NEGATIVE_DIVISOR;
+      if (!branchfree) {
+        magic = -magic;
+      }
+      if (DEBUG) {
+        std::cout << "[SR] Negative divisor, magic = " << magic << ", more = " << (int)more << std::endl;
+      }
+    }
+    
+    // 为我们的IR生成提取移位量和标志  
+    int shift = more & 0x3F; // 移除标志，保留移位量（位0-5）
+    bool need_add = (more & LIBDIVIDE_ADD_MARKER) != 0;
+    bool is_negative = (more & LIBDIVIDE_NEGATIVE_DIVISOR) != 0;
+    
+    if (DEBUG) {
+      std::cout << "[SR] Final result: magic = " << magic << ", more = " << (int)more 
+                << " (0x" << std::hex << (int)more << std::dec << ")" << std::endl;
+      std::cout << "[SR] Shift = " << shift << ", need_add = " << need_add 
+                << ", is_negative = " << is_negative << std::endl;
+      
+      // Test the magic number using the correct libdivide algorithm
+      std::cout << "[SR] Testing magic number (libdivide algorithm):" << std::endl;
+      int test_values[] = {1, 7, 37, 100, 999, -1, -7, -37, -100};
+      
+      for (int test_val : test_values) {
+        int64_t quotient;
+        
+        // 实现正确的libdivide算法
+        int64_t product = (int64_t)test_val * magic;
+        int64_t high_bits = product >> 32;
+        
+        if (need_add) {
+          // ADD_MARKER情况：移位前加上被除数
+          // 这是libdivide的关键洞察！
+          high_bits += test_val;
+          quotient = high_bits >> shift;
+        } else {
+          // 正常情况：只是移位
+          quotient = high_bits >> shift;
+        }
+        
+        // 符号修正：这是libdivide有符号除法的关键部分！
+        // 如果被除数为负，商需要加1来匹配C语言的截断除法语义
+        if (test_val < 0) {
+          quotient += 1;
+        }
+        
+        int expected = test_val / divisor;
+        
+        bool correct = (quotient == expected);
+        std::cout << "[SR]   " << test_val << " / " << divisor << " = " << quotient 
+                  << " (expected " << expected << ") " << (correct ? "✓" : "✗") << std::endl;
+      }
+      
+      std::cout << "[SR] ===== End magic computation =====" << std::endl;
+    }
+    
+    // 返回魔数、移位量，并在移位中编码ADD_MARKER标志
+    // 我们将使用移位的第6位表示ADD_MARKER，第7位表示负数（如果需要）
+    int encoded_shift = shift;
+    if (need_add) {
+      encoded_shift |= 0x40; // 设置第6位表示ADD_MARKER
+      if (DEBUG) {
+        std::cout << "[SR] Encoding ADD_MARKER in shift: " << encoded_shift << std::endl;
+      }
+    }
+    
+    return {magic, encoded_shift};
+  }
+
 };
 
 }// namespace sysy