[BugFix][Opencl] Explicitly cast min/max operands

src/target/source/codegen_opencl.cc

@@ -478,6 +478,31 @@ void CodeGenOpenCL::VisitExpr_(const FloatImmNode* op, std::ostream& os) {  // N
   }
 }
 
+template <typename T>
+inline void PrintBinaryExpr(const T* op, const char* opstr, std::ostream& os, CodeGenOpenCL* p) {
+  if (op->dtype.lanes() == 1) {
+    os << opstr << "((";
+    p->PrintType(op->a->dtype, os);
+    os << ")";
+    p->PrintExpr(op->a, os);
+    os << ", (";
+    p->PrintType(op->b->dtype, os);
+    os << ")";
+    p->PrintExpr(op->b, os);
+    os << ')';
+  } else {
+    p->PrintVecBinaryOp(opstr, op->dtype, op->a, op->b, os);
+  }
+}
+
+void CodeGenOpenCL::VisitExpr_(const MinNode* op, std::ostream& os) {
+  PrintBinaryExpr(op, "min", os, this);
+}
+
+void CodeGenOpenCL::VisitExpr_(const MaxNode* op, std::ostream& os) {
+  PrintBinaryExpr(op, "max", os, this);
+}
+
 void CodeGenOpenCL::SetTextureScope(
     const std::unordered_map<const VarNode*, std::string>& scope) {  // NOLINT(*)
   for (auto& texture : scope) {

src/target/source/codegen_opencl.h

@@ -65,6 +65,10 @@ class CodeGenOpenCL final : public CodeGenC {
   void VisitExpr_(const FloatImmNode* op, std::ostream& os) final;   // NOLINT(*)
   void VisitStmt_(const StoreNode* op) final;                        // NOLINT(*)
 
+  // overload min and max to avoid ambiguous call errors
+  void VisitExpr_(const MinNode* op, std::ostream& os) final;
+  void VisitExpr_(const MaxNode* op, std::ostream& os) final;
+
  private:
   // whether enable fp16 and fp64 extension
   bool enable_fp16_{false};

tests/python/unittest/test_target_codegen_opencl.py

@@ -142,4 +142,5 @@ def check_erf(dev, n, dtype):
 if __name__ == "__main__":
     test_opencl_ternary_expression()
     test_opencl_inf_nan()
+    test_opencl_max()
     test_opencl_erf()