Tolerate empty FunctionBases in critical path analysis and benchmark_…

…main. PiperOrigin-RevId: 683702773
google · Oct 8, 2024 · 600dfac · 600dfac
1 parent 6a04649
commit 600dfac
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Showing 3 changed files with 21 additions and 5 deletions.
diff --git a/xls/dev_tools/benchmark_main.cc b/xls/dev_tools/benchmark_main.cc
@@ -256,8 +256,9 @@ absl::Status PrintCriticalPath(
     const synthesis::SynthesizedDelayDiffByStage& delay_diff) {
   const std::vector<CriticalPathEntry>& critical_path =
       delay_diff.total_diff.critical_path;
-  std::cout << absl::StrFormat("Critical path delay: %dps\n",
-                               critical_path.front().path_delay_ps);
+  int64_t total_delay =
+      critical_path.empty() ? 0 : critical_path.front().path_delay_ps;
+  std::cout << absl::StrFormat("Critical path delay: %dps\n", total_delay);
   std::cout << absl::StrFormat("Critical path entry count: %d\n",
                                critical_path.size());
 
@@ -283,7 +284,6 @@ absl::Status PrintCriticalPath(
     tally.second += 1;
   }
 
-  int64_t total_delay = critical_path.front().path_delay_ps;
   std::cout << absl::StrFormat("Contribution by op (total %dps):\n",
                                total_delay);
   std::vector<Op> ops(kAllOps.begin(), kAllOps.end());

diff --git a/xls/estimators/delay_model/analyze_critical_path.cc b/xls/estimators/delay_model/analyze_critical_path.cc
@@ -101,10 +101,14 @@ absl::StatusOr<std::vector<CriticalPathEntry>> AnalyzeCriticalPath(
     }
   }
 
-  // Starting with the operation with the longest pat hdelay, walk back up its
+  // `latest_entry` has no value for empty FunctionBases.
+  if (!latest_entry.has_value()) {
+    return std::vector<CriticalPathEntry>();
+  }
+
+  // Starting with the operation with the longest path delay, walk back up its
   // critical path constructing CriticalPathEntry's as we go.
   std::vector<CriticalPathEntry> critical_path;
-  XLS_RET_CHECK(latest_entry.has_value());
   NodeEntry* entry = &(latest_entry.value());
   while (true) {
     critical_path.push_back(CriticalPathEntry{

diff --git a/xls/estimators/delay_model/analyze_critical_path_test.cc b/xls/estimators/delay_model/analyze_critical_path_test.cc
@@ -160,5 +160,17 @@ TEST_F(AnalyzeCriticalPathTest, ProcWithSendReceive) {
                               FieldsAre(m::Literal(Value::Token()), _, _, _)));
 }
 
+TEST_F(AnalyzeCriticalPathTest, EmptyProc) {
+  auto p = CreatePackage();
+  ProcBuilder b(TestName(), p.get());
+  XLS_ASSERT_OK_AND_ASSIGN(Proc * proc, b.Build({}));
+
+  XLS_ASSERT_OK_AND_ASSIGN(
+      std::vector<CriticalPathEntry> cp,
+      AnalyzeCriticalPath(proc, /*clock_period_ps=*/std::nullopt,
+                          *delay_estimator_));
+  EXPECT_TRUE(cp.empty());
+}
+
 }  // namespace
 }  // namespace xls