[llvm] [llvm][ctx_profile] Add instrumentation lowering (PR #90821)

[Mircea Trofin via llvm-commits]

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@@ -22,3 +31,295 @@ static cl::list<std::string> ContextRoots(
 bool PGOCtxProfLoweringPass::isContextualIRPGOEnabled() {
   return !ContextRoots.empty();
 }
+
+// the names of symbols we expect in compiler-rt. Using a namespace for
+// readability.
+namespace CompilerRtAPINames {
+static auto StartCtx = "__llvm_ctx_profile_start_context";
+static auto ReleaseCtx = "__llvm_ctx_profile_release_context";
+static auto GetCtx = "__llvm_ctx_profile_get_context";
+static auto ExpectedCalleeTLS = "__llvm_ctx_profile_expected_callee";
+static auto CallsiteTLS = "__llvm_ctx_profile_callsite";
+} // namespace CompilerRtAPINames
+
+namespace {
+// The lowering logic and state.
+class CtxInstrumentationLowerer final {
+  Module &M;
+  ModuleAnalysisManager &MAM;
+  Type *ContextNodeTy = nullptr;
+  Type *ContextRootTy = nullptr;
+
+  DenseMap<const Function *, Constant *> ContextRootMap;
+  Function *StartCtx = nullptr;
+  Function *GetCtx = nullptr;
+  Function *ReleaseCtx = nullptr;
+  GlobalVariable *ExpectedCalleeTLS = nullptr;
+  GlobalVariable *CallsiteInfoTLS = nullptr;
+
+public:
+  CtxInstrumentationLowerer(Module &M, ModuleAnalysisManager &MAM);
+  void lowerFunction(Function &F);
+};
+
+std::pair<uint32_t, uint32_t> getNrCountersAndCallsites(const Function &F) {
+  uint32_t NrCounters = 0;
+  uint32_t NrCallsites = 0;
+  for (const auto &BB : F) {
+    for (const auto &I : BB) {
+      if (const auto *Incr = dyn_cast<InstrProfIncrementInst>(&I)) {
+        if (!NrCounters)
+          NrCounters =
+              static_cast<uint32_t>(Incr->getNumCounters()->getZExtValue());
+      } else if (const auto *CSIntr = dyn_cast<InstrProfCallsite>(&I)) {
+        if (!NrCallsites)
+          NrCallsites =
+              static_cast<uint32_t>(CSIntr->getNumCounters()->getZExtValue());
+      }
+      if (NrCounters && NrCallsites)
+        return std::make_pair(NrCounters, NrCallsites);
+    }
+  }
+  return {0, 0};
+}
+} // namespace
+
+// set up tie-in with compiler-rt.
+// NOTE!!!
+// These have to match compiler-rt/lib/ctx_profile/CtxInstrProfiling.h
----------------
mtrofin wrote:

Note: this is in PR #89838 

https://github.com/llvm/llvm-project/pull/90821