[Profiling] Speed up unittests by ~5x

[vsk]

Summary

I noticed that this particular unit test takes a relatively long time to run. Is it OK to shorten it?

[davidxl]

lgtm

[dblaikie]

If we're asking the question - why does this need to be 1024? What's the
specific purpose of the iteration? (why would 1 be too few iterations, for
example?)

[vsk]

Address some of @dblaikie's concerns:

• Only test doCompression = true.
• Move away from a statistical approach.

[vsk]

• Rangify loops.

[davidxl]

please do not remove the no compression path. I think we should just keep your original change of making the iteration to a smaller number. With the latest change plus 1024 iteration, the test time is ~20ms. I am ok with shorten the iteration further if we think 20ms is too costly.

[davidxl]

I took the liberty to further reduce the test time down to ~6ms.

[vsk]

Deferring to David's preference on this one.

unittests/ProfileData/InstrProfTest.cpp

 }
 
 TEST_P(MaybeSparseInstrProfTest, instr_prof_symtab_compression_test) {
-  std::vector<std::string> FuncNames1;
-  std::vector<std::string> FuncNames2;
-  for (int I = 0; I < 10 * 1024; I++) {
-    std::string str;
-    raw_string_ostream OS(str);
-    OS << "func_" << I;
-    FuncNames1.push_back(OS.str());
-    str.clear();
-    OS << "fooooooooooooooo_" << I;
-    FuncNames1.push_back(OS.str());
-    str.clear();
-    OS << "BAR_" << I;
-    FuncNames2.push_back(OS.str());
-    str.clear();
-    OS << "BlahblahBlahblahBar_" << I;
-    FuncNames2.push_back(OS.str());
-  }
-
-  for (bool DoCompression : {false, true}) {
-    // Compressing:
-    std::string FuncNameStrings1;
-    collectPGOFuncNameStrings(
-        FuncNames1, (DoCompression && zlib::isAvailable()), FuncNameStrings1);
-
-    // Compressing:
-    std::string FuncNameStrings2;
-    collectPGOFuncNameStrings(
-        FuncNames2, (DoCompression && zlib::isAvailable()), FuncNameStrings2);
-
-    for (int Padding = 0; Padding < 3; Padding++) {
-      // Join with paddings:
-      std::string FuncNameStrings = FuncNameStrings1;
-      for (int P = 0; P < Padding; P++) {
-        FuncNameStrings.push_back('\0');
-      }
-      FuncNameStrings += FuncNameStrings2;
-
-      // Now decompress:
-      InstrProfSymtab Symtab;
-      Symtab.create(StringRef(FuncNameStrings));
-
-      // Now do the checks:
-      // First sampling some data points:
-      StringRef R = Symtab.getFuncName(IndexedInstrProf::ComputeHash(FuncNames1[0]));
-      ASSERT_EQ(StringRef("func_0"), R);
-      R = Symtab.getFuncName(IndexedInstrProf::ComputeHash(FuncNames1[1]));
-      ASSERT_EQ(StringRef("fooooooooooooooo_0"), R);
-      R = Symtab.getFuncName(IndexedInstrProf::ComputeHash(FuncNames1[998]));
-      ASSERT_EQ(StringRef("func_499"), R);
-      R = Symtab.getFuncName(IndexedInstrProf::ComputeHash(FuncNames1[999]));
-      ASSERT_EQ(StringRef("fooooooooooooooo_499"), R);
-      R = Symtab.getFuncName(IndexedInstrProf::ComputeHash(FuncNames2[100]));
-      ASSERT_EQ(StringRef("BAR_50"), R);
-      R = Symtab.getFuncName(IndexedInstrProf::ComputeHash(FuncNames2[101]));
-      ASSERT_EQ(StringRef("BlahblahBlahblahBar_50"), R);
-      for (int I = 0; I < 10 * 1024; I++) {
-        std::string N[4];
-        N[0] = FuncNames1[2 * I];
-        N[1] = FuncNames1[2 * I + 1];
-        N[2] = FuncNames2[2 * I];
-        N[3] = FuncNames2[2 * I + 1];
-        for (int J = 0; J < 4; J++) {
-          StringRef R = Symtab.getFuncName(IndexedInstrProf::ComputeHash(N[J]));
-          ASSERT_EQ(StringRef(N[J]), R);
-        }
-      }
-    }
+  if (!zlib::isAvailable())
+    return;
+
+  std::string NamesStr;
+  std::vector<std::string> Names = {"foo", "bar", "baz"};
+  collectPGOFuncNameStrings(Names, /*doCompression=*/ true, NamesStr);
+
+  for (int Padding : {0, 1, 2, 3}) {
+    // Join with padding:
+    std::string NamesStrPadded = NamesStr;
+    NamesStrPadded.resize(NamesStr.size() + Padding, '\0');
+
+    // Now decompress the function names:
+    InstrProfSymtab Symtab;
+    Symtab.create(StringRef(NamesStrPadded));
+
+    // Check that we get the function names back:
+    for (auto &Name : Names)
+      ASSERT_EQ(StringRef(Name),
+                Symtab.getFuncName(IndexedInstrProf::ComputeHash(Name)));
   }
 }