fix bug in find_concat_op when input broadcasts are on different axes (…

…#3242)

src/simplify_algebra.cpp

@@ -809,6 +809,18 @@ struct find_concat_op
                op.attributes().contains("pointwise");
     }
 
+    static bool is_valid_concat(std::vector<instruction_ref> ins, size_t axis)
+    {
+        auto concat_lens = ins.front()->get_shape().lens();
+        concat_lens.erase(concat_lens.begin() + axis);
+
+        return std::all_of(ins.begin(), ins.end(), [&](auto i) {
+            auto lens = i->get_shape().lens();
+            lens.erase(lens.begin() + axis);
+            return lens == concat_lens;
+        });
+    }
+
     void apply(module& m, const match::matcher_result& r) const
     {
         auto ins  = r.result;
@@ -852,6 +864,8 @@ struct find_concat_op
                 std::transform(start, last, std::back_inserter(inputs), [&](auto j) {
                     return j->inputs().at(i);
                 });
+                if(not is_valid_concat(inputs, iaxis))
+                    return {start, last};
                 auto concat =
                     m.insert_instruction(ins, make_op("concat", {{"axis", iaxis}}), inputs);
                 concats.push_back(concat);

test/simplify_algebra_test.cpp

@@ -3999,4 +3999,25 @@ TEST_CASE(conv_concat_group)
     EXPECT(m1.sort() == m2.sort());
 }
 
+TEST_CASE(find_concat_different_broadcast_axes)
+{
+    migraphx::shape s1{migraphx::shape::float_type, {128, 1, 1, 1, 1}};
+    migraphx::shape s2{migraphx::shape::float_type, {1, 3, 1, 1, 1}};
+    migraphx::module m1;
+    {
+        auto l1  = m1.add_literal(migraphx::generate_literal(s1, 1));
+        auto l2  = m1.add_literal(migraphx::generate_literal(s2, 2));
+        auto bc1 = m1.add_instruction(
+            migraphx::make_op("multibroadcast", {{"out_lens", {128, 3, 224, 224, 1}}}), l1);
+        auto bc2 = m1.add_instruction(
+            migraphx::make_op("multibroadcast", {{"out_lens", {128, 3, 224, 224, 1}}}), l2);
+        auto cat = m1.add_instruction(migraphx::make_op("concat", {{"axis", 4}}), bc1, bc2);
+        m1.add_return({cat});
+    };
+
+    migraphx::module m2 = m1;
+    run_pass(m1);
+    EXPECT(m1.sort() == m2.sort());
+}
+
 int main(int argc, const char* argv[]) { test::run(argc, argv); }