tests : use backend base name for fusion baseline output

The fusion test is invoked with a specific device name (e.g. MTL0), but
its output - the recorded baseline and the header it writes - should be
named after the backend base name (e.g. MTL, via ggml_backend_reg_name),
since the counters depend on the backend, not on the specific device
index. Rename the committed baseline to MTL.tsv.

Assisted-by: pi:llama.cpp/DeepSeek-V4-Flash-0731

tests/CMakeLists.txt

@@ -252,7 +252,7 @@ if (NOT WIN32 OR NOT BUILD_SHARED_LIBS)
     llama_test(
         test-fusion
         LABEL main
-        ARGS --models "${MODEL_DIR}" --device MTL0 --check "${PROJECT_SOURCE_DIR}/tests/fusion/MTL0.tsv"
+        ARGS --models "${MODEL_DIR}" --device MTL0 --check "${PROJECT_SOURCE_DIR}/tests/fusion/MTL.tsv"
     )
     set_tests_properties(test-fusion PROPERTIES FIXTURES_REQUIRED generate-models)
 endif()

tests/fusion/MTL.tsv

@@ -1,4 +1,4 @@
-# test-fusion baseline for backend MTL0
+# test-fusion baseline for device MTL
 # arch	moe	mode	label	count
 arcee	0	prefill	RMS_NORM+MUL	5
 arcee	0	decode	RMS_NORM+MUL	80

tests/test-fusion.cpp

@@ -296,6 +296,10 @@ int main(int argc, char ** argv) {
     // mechanism; a backend that does not adopt fusion debugging exports none of them
     auto * reg = ggml_backend_dev_backend_reg(dev);
 
+    // output naming uses the backend base name (e.g. "MTL") rather than the specific device
+    // name (e.g. "MTL0") the test was invoked with
+    const std::string base_name = ggml_backend_reg_name(reg);
+
     auto api_stats_init  = (fusion_stats_init_t)  ggml_backend_reg_get_proc_address(reg, "ggml_backend_fusion_stats_init");
     auto api_stats_reset = (fusion_stats_reset_t) ggml_backend_reg_get_proc_address(reg, "ggml_backend_fusion_stats_reset");
     auto api_stats_get   = (fusion_stats_get_t)   ggml_backend_reg_get_proc_address(reg, "ggml_backend_fusion_stats_get");
@@ -342,7 +346,7 @@ int main(int argc, char ** argv) {
 
     std::vector<fusion_row> rows;
 
-    LOG_INF("%s: running fusion test over %zu models on '%s'\n", __func__, models.size(), device_name.c_str());
+    LOG_INF("%s: running fusion test over %zu models on '%s'\n", __func__, models.size(), base_name.c_str());
 
     const size_t seed = 1;
 
@@ -454,7 +458,7 @@ int main(int argc, char ** argv) {
         std::ofstream out(record_path);
         std::ostream & os = record_path.empty() ? std::cout : out;
         if (!record_path.empty()) {
-            os << "# test-fusion baseline for device " << device_name << "\n";
+            os << "# test-fusion baseline for device " << base_name << "\n";
             os << "# arch\tmoe\tmode\tlabel\tcount\n";
         }