[llvm] (Decomp of #5251 7/n) Change the way to record the time of offline cache

taichi/runtime/llvm/llvm_aot_module_builder.cpp

@@ -26,6 +26,8 @@ void LlvmAotModuleBuilder::add_per_backend(const std::string &identifier,
   kcache.owned_module = std::move(compiled.module);
   kcache.args = infer_launch_args(kernel);
   kcache.offloaded_task_list = std::move(compiled.tasks);
+  kcache.last_used_at = std::time(nullptr);
+  kcache.created_at = std::time(nullptr);
   cache_.kernels[identifier] = std::move(kcache);
 }
 
@@ -64,7 +66,10 @@ void LlvmAotModuleBuilder::add_field_per_backend(const std::string &identifier,
 void LlvmAotModuleBuilder::add_compiled_kernel(aot::Kernel *kernel) {
   auto *kernel_impl = dynamic_cast<llvm_aot::KernelImpl *>(kernel);
   TI_ASSERT(kernel_impl);
-
+  if (!kernel_impl->kernel_data_.created_at) {
+    kernel_impl->kernel_data_.last_used_at = std::time(nullptr);
+    kernel_impl->kernel_data_.created_at = std::time(nullptr);
+  }
   const std::string &kernel_name = kernel_impl->kernel_name_;
   if (cache_.kernels.find(kernel_name) == cache_.kernels.end()) {
     cache_.kernels[kernel_name] = std::move(kernel_impl->kernel_data_);

taichi/runtime/llvm/llvm_offline_cache.cpp

@@ -115,6 +115,10 @@ bool LlvmOfflineCacheFileReader::get_kernel_cache(
     kernel_data.module = kernel_data.owned_module.get();
   }
 
+  kernel_data.last_used_at = std::time(nullptr);
+
+  res.created_at = kernel_data.created_at;
+  res.last_used_at = kernel_data.last_used_at;
   res.kernel_key = key;
   res.args = kernel_data.args;
   res.offloaded_task_list = kernel_data.offloaded_task_list;
@@ -146,7 +150,6 @@ void LlvmOfflineCacheFileWriter::dump(const std::string &path,
                                       LlvmOfflineCache::Format format,
                                       bool merge_with_old) {
   taichi::create_directories(path);
-  std::time_t now = std::time(nullptr);
   std::size_t new_kernels_size = 0;  // bytes
 
   for (auto &[k, v] : data_.kernels) {
@@ -185,8 +188,8 @@ void LlvmOfflineCacheFileWriter::dump(const std::string &path,
     }
 
     // Set meta info
-    v.created_at = now;
-    v.last_used_at = now;
+    TI_ASSERT(v.created_at);
+    TI_ASSERT(v.last_used_at);
     v.size = size;
     TI_ASSERT(v.size > 0);
     new_kernels_size += v.size;

taichi/runtime/program_impls/llvm/llvm_program.cpp

@@ -126,6 +126,8 @@ void LlvmProgramImpl::cache_kernel(
     return;
   }
   auto &kernel_cache = cache_data_->kernels[kernel_key];
+  kernel_cache.created_at = std::time(nullptr);
+  kernel_cache.last_used_at = std::time(nullptr);
   kernel_cache.kernel_key = kernel_key;
   kernel_cache.owned_module = llvm::CloneModule(*module);
   kernel_cache.args = std::move(args);

tests/cpp/llvm/llvm_offline_cache_test.cpp

@@ -96,6 +96,8 @@ TEST_P(LlvmOfflineCacheTest, ReadWrite) {
 
     LlvmOfflineCacheFileWriter writer;
     LlvmOfflineCache::KernelCacheData kcache;
+    kcache.created_at = 1;
+    kcache.last_used_at = 1;
     kcache.kernel_key = kKernelName;
     kcache.owned_module = make_module(*llvm_ctx);
     kcache.module = kcache.owned_module.get();