diff --git a/App/lib/core/Gen/Expr/ExprGenBase.vp b/App/lib/core/Gen/Expr/ExprGenBase.vp
index 1062c27..7d5fa6c 100644
--- a/App/lib/core/Gen/Expr/ExprGenBase.vp
+++ b/App/lib/core/Gen/Expr/ExprGenBase.vp
@@ -121,6 +121,21 @@ novirtual class ExprGenBase:
     def get_ptr_level(self, ty: mlirlite.LLVMType*) -> int:
         """Compute pointer level (0=non-ptr, 1=ptr, 2=ptr-to-ptr); delegates to TSpec.SpecTypePtrLevel."""
         return TSpec.SpecTypePtrLevel(ty)
+    # _const_fits_int_type - 编译期整型常量的值能否**无损**落进目标整型位宽。
+    # 有符号或无符号任一解释放得下即算「放得下」（位型不变）；用于二元运算按常量适配另一侧位宽。
+    def _const_fits_int_type(self, val: mlirlite.Value*, target_ty: mlirlite.LLVMType*) -> int:
+        """1 = the integer constant's value fits the target integer width losslessly; else 0."""
+        if val is None or target_ty is None or val.IsConst != 1: return 0
+        bits: int = self.get_llvm_type_bits(target_ty)
+        if bits <= 0 or bits > 63: return 0
+        v: int64 = val.IntVal
+        lo: int64 = -(int64(1) << (bits - 1))
+        hi: int64 = (int64(1) << (bits - 1)) - 1
+        if v >= lo and v <= hi: return 1
+        if v >= 0:
+            if bits == 63: return 1
+            if v <= (int64(1) << bits) - 1: return 1
+        return 0
     # _is_zero_int_literal - is the AST node the integer literal 0?
     # Used for ptr != 0 / ptr == 0, where 0 means NULL and is allowed.
     def _is_zero_int_literal(self, node: ast.AST*) -> int:
diff --git a/App/lib/core/Gen/Expr/ExprGenOps.vp b/App/lib/core/Gen/Expr/ExprGenOps.vp
index 5985c58..a875a3e 100644
--- a/App/lib/core/Gen/Expr/ExprGenOps.vp
+++ b/App/lib/core/Gen/Expr/ExprGenOps.vp
@@ -1230,10 +1230,14 @@ novirtual class ExprGenOps(ExprGenBase.ExprGenBase):
                 rhs_bits = 32
 
         if lhs_bits > rhs_bits:
-            if self.should_zext_widen(pool, rhs, lhs, rhs_node, trans) != 0: rhs = mlirlite.build_zext(builder, rhs, lhs.Ty)
+            # 宽侧是「值能无损落进窄侧」的编译期常量时，把**常量**降到窄侧类型（C 语义：常量优先适配另一侧），
+            # 否则 `crc(u32) ^ 0xFFFFFFFF(i64)` 会把 crc 抬成 64 位，结果再赋回 32 位时报隐式窄化。
+            if self._const_fits_int_type(lhs, rhs.Ty) != 0: lhs = self.coerce_to_type(builder, lhs, rhs.Ty, node, trans)
+            elif self.should_zext_widen(pool, rhs, lhs, rhs_node, trans) != 0: rhs = mlirlite.build_zext(builder, rhs, lhs.Ty)
             else: rhs = self.coerce_to_type(builder, rhs, lhs.Ty, node, trans)
         elif rhs_bits > lhs_bits:
-            if self.should_zext_widen(pool, lhs, rhs, lhs_node, trans) != 0: lhs = mlirlite.build_zext(builder, lhs, rhs.Ty)
+            if self._const_fits_int_type(rhs, lhs.Ty) != 0: rhs = self.coerce_to_type(builder, rhs, lhs.Ty, node, trans)
+            elif self.should_zext_widen(pool, lhs, rhs, lhs_node, trans) != 0: lhs = mlirlite.build_zext(builder, lhs, rhs.Ty)
             else: lhs = self.coerce_to_type(builder, lhs, rhs.Ty, node, trans)
 
         # Bitwise type safety: when both sides are pointers (lhs_bits==0 and rhs_bits==0), bitwise ops are illegal (LLVM