feat(pnnx): convert prelu[num_parameters=1] to leakyrelu, so that it can be fused with conv

Author: w43322

tools/pnnx/src/CMakeLists.txt

@@ -412,9 +412,10 @@ set(pnnx_pass_level5_SRCS
 set(pnnx_pass_ncnn_SRCS
     pass_ncnn/convert_attribute.cpp
     pass_ncnn/convert_custom_op.cpp
-    pass_ncnn/convert_module_op.cpp
     pass_ncnn/convert_half_to_float.cpp
     pass_ncnn/convert_input.cpp
+    pass_ncnn/convert_module_op.cpp
+    pass_ncnn/convert_prelu.cpp
     pass_ncnn/convert_reshape_interp_expression.cpp
     pass_ncnn/convert_slice_expression.cpp
     pass_ncnn/convert_torch_cat.cpp

tools/pnnx/src/pass_ncnn/convert_prelu.cpp

@@ -0,0 +1,45 @@
+// Copyright 2025 Tencent
+// SPDX-License-Identifier: BSD-3-Clause
+
+#include "pass_ncnn.h"
+
+namespace pnnx {
+
+namespace ncnn {
+
+class convert_prelu : public GraphRewriterPass
+{
+public:
+    const char* match_pattern_graph() const
+    {
+        return R"PNNXIR(7767517
+3 2
+pnnx.Input              input       0 1 input
+PReLU                   op_0        1 1 input out 0=1
+pnnx.Output             output      1 0 out
+)PNNXIR";
+    }
+
+    const char* type_str() const
+    {
+        return "ReLU";
+    }
+
+    const char* name_str() const
+    {
+        return "relu";
+    }
+
+    void write(Operator* op, const std::map<std::string, Parameter>& captured_params, const std::map<std::string, Attribute>& captured_attrs) const
+    {
+        const Attribute& slope = captured_attrs.at("op_0.0");
+        op->params["0"] = slope.get_float32_data()[0];
+    }
+};
+
+REGISTER_GLOBAL_PNNX_NCNN_GRAPH_REWRITER_PASS(convert_prelu, 99)
+
+} // namespace ncnn
+
+} // namespace pnnx
+