[PATCH] D31519: [XRay][tools] Remove some assertions in llvm-xray graph

[Dean Michael Berris via Phabricator via llvm-commits]

dberris created this revision.

Assertions assuming that function calls may not have zero durations do
not seem to hold in the wild. There are valid cases where the conversion
of the tsc counters end up becoming zero-length durations. These
assertions don't really hold and the algorithms don't need those to be
true for them to work.


https://reviews.llvm.org/D31519

Files:
  test/tools/llvm-xray/X86/graph-zero-latency-calls.yaml
  tools/llvm-xray/xray-graph.cc


Index: tools/llvm-xray/xray-graph.cc
===================================================================
--- tools/llvm-xray/xray-graph.cc
+++ tools/llvm-xray/xray-graph.cc
@@ -259,7 +259,7 @@
 
 template <typename U>
 void GraphRenderer::getStats(U begin, U end, GraphRenderer::TimeStat &S) {
-  assert(begin != end);
+  if (begin == end) return;
   std::ptrdiff_t MedianOff = S.Count / 2;
   std::nth_element(begin, begin + MedianOff, end);
   S.Median = *(begin + MedianOff);
@@ -287,25 +287,20 @@
   for (auto &E : G.edges()) {
     auto &A = E.second;
     assert(!A.Timings.empty());
-    assert((A.Timings[0] > 0));
     getStats(A.Timings.begin(), A.Timings.end(), A.S);
-    assert(A.S.Sum > 0);
     updateMaxStats(A.S, G.GraphEdgeMax);
   }
 }
 
 void GraphRenderer::calculateVertexStatistics() {
   std::vector<uint64_t> TempTimings;
   for (auto &V : G.vertices()) {
-    assert((V.first == 0 || G[V.first].S.Sum != 0) &&
-           "Every non-root vertex should have at least one call");
     if (V.first != 0) {
       for (auto &E : G.inEdges(V.first)) {
         auto &A = E.second;
         TempTimings.insert(TempTimings.end(), A.Timings.begin(),
                            A.Timings.end());
       }
-      assert(!TempTimings.empty() && TempTimings[0] > 0);
       getStats(TempTimings.begin(), TempTimings.end(), G[V.first].S);
       updateMaxStats(G[V.first].S, G.GraphVertexMax);
       TempTimings.clear();
Index: test/tools/llvm-xray/X86/graph-zero-latency-calls.yaml
===================================================================
--- /dev/null
+++ test/tools/llvm-xray/X86/graph-zero-latency-calls.yaml
@@ -0,0 +1,20 @@
+#RUN: llvm-xray graph %s -o - -m %S/Inputs/simple-instrmap.yaml | FileCheck %s
+
+---
+header:
+  version: 1
+  type: 0
+  constant-tsc: true
+  nonstop-tsc: true
+  cycle-frequency: 2601000000
+records:
+  - { type: 0, func-id: 1, cpu: 1, thread: 111, kind: function-enter, tsc: 10001 }
+  - { type: 0, func-id: 2, cpu: 1, thread: 111, kind: function-enter, tsc: 10002 }
+  - { type: 0, func-id: 2, cpu: 1, thread: 111, kind: function-exit, tsc: 10002 }
+  - { type: 0, func-id: 1, cpu: 1, thread: 111, kind: function-exit, tsc: 10100 }
+...
+
+#CHECK:     digraph xray {
+#CHECK-DAG:   F0 -> F1 [{{.*}}];
+#CHECK-DAG:   F1 -> F2 [{{.*}}];
+#CHECK-DAG: }


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