[Bugfix][Transform] Preserve symbolic variables in FuseOps

src/relax/transform/fuse_ops.cc

@@ -1203,10 +1203,11 @@ class CompositeFunctionAnnotator : public ExprMutator {
             func->GetAttr<String>(attr::kCodegen).defined()) {
           continue;
         }
-        auto new_body = VisitExpr(func->body);
+
+        auto new_body = VisitWithNewScope(func->body, func->params);
         if (!new_body.same_as(func->body)) {
-          auto new_func = Function(func->params, VisitExpr(func->body), func->ret_struct_info,
-                                   func->is_pure, func->attrs, func->span);
+          auto new_func = Function(func->params, new_body, func->ret_struct_info, func->is_pure,
+                                   func->attrs, func->span);
           builder_->UpdateFunction(entry.first, new_func);
         }
       }

tests/python/relax/test_transform_fuse_ops_by_pattern.py

@@ -1130,5 +1130,92 @@ def test_error_on_repeated_variable_definitions():
         relax.transform.FuseOpsByPattern(patterns)(mod)
 
 
+def test_matmul_symbolic_var():
+    @I.ir_module
+    class Before:
+        @R.function
+        def main(
+            x: R.Tensor(["batch_size", 1024], "float16"),
+            w1: R.Tensor([1024, 1024], "float16"),
+            w2: R.Tensor([1024, "M"], "float16"),
+        ):
+            with R.dataflow():
+                matmul1 = R.matmul(x, w1)
+                matmul2 = R.matmul(x, w2)
+                out = (matmul1, matmul2)
+                R.output(out)
+            return out
+
+    @I.ir_module
+    class Expected:
+        @R.function
+        def main(
+            x: R.Tensor(["batch_size", 1024], "float16"),
+            w1: R.Tensor([1024, 1024], "float16"),
+            w2: R.Tensor([1024, "M"], "float16"),
+        ) -> R.Tuple(
+            R.Tensor(["batch_size", 1024], "float16"),
+            R.Tensor(["batch_size", "M"], "float16"),
+        ):
+            cls = Expected
+            with R.dataflow():
+                matmul1 = cls.fused_relax_matmul_cublas(x, w1)
+                matmul2 = cls.fused_relax_matmul1_cublas(x, w2)
+                out = (matmul1, matmul2)
+                R.output(out)
+            return out
+
+        @R.function
+        def fused_relax_matmul_cublas(
+            x: R.Tensor(["batch_size", 1024], "float16"),
+            w1: R.Tensor([1024, 1024], "float16"),
+        ) -> R.Tensor(["batch_size", 1024], "float16"):
+            batch_size = T.int64()
+            R.func_attr({"Codegen": "cublas"})
+
+            @R.function
+            def inner_func(
+                x: R.Tensor([batch_size, 1024], "float16"),
+                w1: R.Tensor([1024, 1024], "float16"),
+            ) -> R.Tensor([batch_size, 1024], "float16"):
+                R.func_attr({"Composite": "cublas.matmul"})
+                with R.dataflow():
+                    out = R.matmul(x, w1)
+                    R.output(out)
+                return out
+
+            out = inner_func(x, w1)
+            return out
+
+        @R.function
+        def fused_relax_matmul1_cublas(
+            x: R.Tensor(["batch_size", 1024], "float16"),
+            w2: R.Tensor([1024, "M"], "float16"),
+        ) -> R.Tensor(["batch_size", "M"], "float16"):
+            batch_size = T.int64()
+            M = T.int64()
+            R.func_attr({"Codegen": "cublas"})
+
+            @R.function
+            def inner_func(
+                x: R.Tensor([batch_size, 1024], "float16"),
+                w2: R.Tensor((1024, M), "float16"),
+            ) -> R.Tensor([batch_size, M], "float16"):
+                R.func_attr({"Composite": "cublas.matmul"})
+                with R.dataflow():
+                    out = R.matmul(x, w2)
+                    R.output(out)
+                return out
+
+            out = inner_func(x, w2)
+            return out
+
+    patterns = relax.backend.pattern_registry.get_patterns_with_prefix("cublas.matmul")
+    After = relax.transform.FuseOpsByPattern(patterns, bind_constants=False, annotate_codegen=True)(
+        Before
+    )
+    tvm.ir.assert_structural_equal(Expected, After)
+
+
 if __name__ == "__main__":
     pytest.main([__file__])