Merge branch 'backend-divopt' into midend

src/midend/SysYIRGenerator.cpp

@@ -15,6 +15,29 @@
 using namespace std;
 namespace sysy {
 
+std::pair<long long, int> calculate_signed_magic(int d) {
+    if (d == 0) throw std::runtime_error("Division by zero");
+    if (d == 1 || d == -1) return {0, 0}; // Not used by strength reduction
+
+    int k = 0;
+    unsigned int ad = (d > 0) ? d : -d;
+    unsigned int temp = ad;
+    while (temp > 0) {
+        temp >>= 1;
+        k++;
+    }
+    if ((ad & (ad - 1)) == 0) { // if power of 2
+        k--;
+    }
+
+    unsigned __int128 m_val = 1;
+    m_val <<= (32 + k - 1);
+    unsigned __int128 m_prime = m_val / ad;
+    long long m = m_prime + 1;
+
+    return {m, k};
+}
+
 
 // std::vector<Value*> BinaryValueStack;  ///< 用于存储value的栈
 // std::vector<int> BinaryOpStack;  ///< 用于存储二元表达式的操作符栈 
@@ -249,7 +272,26 @@ void SysYIRGenerator::compute() {
             case BinaryOp::ADD: resultValue = builder.createAddInst(lhs, rhs); break;
             case BinaryOp::SUB: resultValue = builder.createSubInst(lhs, rhs); break;
             case BinaryOp::MUL: resultValue = builder.createMulInst(lhs, rhs); break;
-            case BinaryOp::DIV: resultValue = builder.createDivInst(lhs, rhs); break;
+            case BinaryOp::DIV: {
+              ConstantInteger *rhsConst = dynamic_cast<ConstantInteger *>(rhs);
+              if (rhsConst) {
+                int divisor = rhsConst->getInt();
+                if (divisor > 0 && (divisor & (divisor - 1)) == 0) {
+                  int shift = 0;
+                  int temp = divisor;
+                  while (temp > 1) {
+                    temp >>= 1;
+                    shift++;
+                  }
+                  resultValue = builder.createSRAInst(lhs, ConstantInteger::get(shift));
+                } else {
+                  resultValue = builder.createDivInst(lhs, rhs);
+                }
+              } else {
+                resultValue = builder.createDivInst(lhs, rhs);
+              }
+              break;
+            }
             case BinaryOp::MOD: resultValue = builder.createRemInst(lhs, rhs); break;
             }
           } else if (commonType == Type::getFloatType()) {