[compiler-rt] [llvm] [ctxprof] root autodetection mechanism (PR #133147)

[Snehasish Kumar via llvm-commits]

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@@ -0,0 +1,188 @@
+// Root autodetection test for contextual profiling
+//
+// Copy the header defining ContextNode.
+// RUN: mkdir -p %t_include
+// RUN: cp %llvm_src/include/llvm/ProfileData/CtxInstrContextNode.h %t_include/
+//
+// Compile with ctx instrumentation "on". We use -profile-context-root as signal
+// that we want contextual profiling, but we can specify anything there, that
+// won't be matched with any function, and result in the behavior we are aiming
+// for here.
+//
+// RUN: %clangxx %s %ctxprofilelib -I%t_include -O2 -o %t.bin \
+// RUN:   -mllvm -profile-context-root="<autodetect>" -g -Wl,-export-dynamic
+//
+// Run the binary, and observe the profile fetch handler's output.
+// RUN %t.bin | FileCheck %s
+
+#include "CtxInstrContextNode.h"
+#include <atomic>
+#include <cstdio>
+#include <iostream>
+#include <thread>
+
+using namespace llvm::ctx_profile;
+extern "C" void __llvm_ctx_profile_start_collection(unsigned);
+extern "C" bool __llvm_ctx_profile_fetch(ProfileWriter &);
+
+// avoid name mangling
+extern "C" {
+__attribute__((noinline)) void anotherFunction() {}
+__attribute__((noinline)) void mock1() {}
+__attribute__((noinline)) void mock2() {}
+__attribute__((noinline)) void someFunction(int I) {
+  if (I % 2)
+    mock1();
+  else
+    mock2();
+  anotherFunction();
+}
+
+// block inlining because the pre-inliner otherwise will inline this - it's
+// too small.
+__attribute__((noinline)) void theRoot() {
+  someFunction(1);
+#pragma nounroll
+  for (auto I = 0; I < 2; ++I) {
+    someFunction(I);
+  }
+  anotherFunction();
+}
+}
+
+class TestProfileWriter : public ProfileWriter {
+  void printProfile(const ContextNode &Node, const std::string &Indent,
+                    const std::string &Increment) {
+    std::cout << Indent << "Guid: " << Node.guid() << std::endl;
+    std::cout << Indent << "Entries: " << Node.entrycount() << std::endl;
+    std::cout << Indent << Node.counters_size() << " counters and "
+              << Node.callsites_size() << " callsites" << std::endl;
+    std::cout << Indent << "Counter values: ";
+    for (uint32_t I = 0U; I < Node.counters_size(); ++I)
+      std::cout << Node.counters()[I] << " ";
+    std::cout << std::endl;
+    for (uint32_t I = 0U; I < Node.callsites_size(); ++I)
+      for (const auto *N = Node.subContexts()[I]; N; N = N->next()) {
+        std::cout << Indent << "At Index " << I << ":" << std::endl;
+        printProfile(*N, Indent + Increment, Increment);
+      }
+  }
+
+  void startContextSection() override {
+    std::cout << "Entered Context Section" << std::endl;
+  }
+
+  void endContextSection() override {
+    std::cout << "Exited Context Section" << std::endl;
+  }
+
+  void writeContextual(const ContextNode &RootNode,
+                       const ContextNode *Unhandled,
+                       uint64_t EntryCount) override {
+    std::cout << "Entering Root " << RootNode.guid()
+              << " with total entry count " << EntryCount << std::endl;
+    for (const auto *P = Unhandled; P; P = P->next())
+      std::cout << "Unhandled GUID: " << P->guid() << " entered "
+                << P->entrycount() << " times" << std::endl;
+    printProfile(RootNode, " ", " ");
+  }
+
+  void startFlatSection() override {
+    std::cout << "Entered Flat Section" << std::endl;
+  }
+
+  void writeFlat(GUID Guid, const uint64_t *Buffer,
+                 size_t BufferSize) override {
+    std::cout << "Flat: " << Guid << " " << Buffer[0];
+    for (size_t I = 1U; I < BufferSize; ++I)
+      std::cout << "," << Buffer[I];
+    std::cout << std::endl;
+  };
+
+  void endFlatSection() override {
+    std::cout << "Exited Flat Section" << std::endl;
+  }
+};
+
+// Guid:3950394326069683896 is anotherFunction
+// Guid:6759619411192316602 is someFunction
+// These are expected to be the auto-detected roots. This is because we cannot
+// discerne (with the current autodetection mechanism) if theRoot
----------------
snehasish wrote:

typo: discern

https://github.com/llvm/llvm-project/pull/133147