[llvm-branch-commits] [llvm] [ctx_prof] Add support for ICP (PR #105469)

[Snehasish Kumar via llvm-branch-commits]

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@@ -572,6 +575,89 @@ CallBase &llvm::promoteCallWithIfThenElse(CallBase &CB, Function *Callee,
   return promoteCall(NewInst, Callee);
 }
 
+CallBase *llvm::promoteCallWithIfThenElse(CallBase &CB, Function &Callee,
+                                          PGOContextualProfile &CtxProf) {
+  assert(CB.isIndirectCall());
+  if (!CtxProf.isFunctionKnown(Callee))
+    return nullptr;
+  auto &Caller = *CB.getParent()->getParent();
+  auto *CSInstr = CtxProfAnalysis::getCallsiteInstrumentation(CB);
+  if (!CSInstr)
+    return nullptr;
+  const auto CSIndex = CSInstr->getIndex()->getZExtValue();
+
+  CallBase &DirectCall = promoteCall(
+      versionCallSite(CB, &Callee, /*BranchWeights=*/nullptr), &Callee);
+  CSInstr->moveBefore(&CB);
+  const auto NewCSID = CtxProf.allocateNextCallsiteIndex(Caller);
+  auto *NewCSInstr = cast<InstrProfCallsite>(CSInstr->clone());
+  NewCSInstr->setIndex(NewCSID);
+  NewCSInstr->setCallee(&Callee);
+  NewCSInstr->insertBefore(&DirectCall);
+  auto &DirectBB = *DirectCall.getParent();
+  auto &IndirectBB = *CB.getParent();
+
+  assert((CtxProfAnalysis::getBBInstrumentation(IndirectBB) == nullptr) &&
+         "The ICP direct BB is new, it shouldn't have instrumentation");
+  assert((CtxProfAnalysis::getBBInstrumentation(DirectBB) == nullptr) &&
+         "The ICP indirect BB is new, it shouldn't have instrumentation");
+
+  // Make the 2 new BBs have counters.
+  const uint32_t DirectID = CtxProf.allocateNextCounterIndex(Caller);
+  const uint32_t IndirectID = CtxProf.allocateNextCounterIndex(Caller);
+  const uint32_t NewCountersSize = IndirectID + 1;
+  auto *EntryBBIns =
+      CtxProfAnalysis::getBBInstrumentation(Caller.getEntryBlock());
+  auto *DirectBBIns = cast<InstrProfCntrInstBase>(EntryBBIns->clone());
+  DirectBBIns->setIndex(DirectID);
+  DirectBBIns->insertInto(&DirectBB, DirectBB.getFirstInsertionPt());
+
+  auto *IndirectBBIns = cast<InstrProfCntrInstBase>(EntryBBIns->clone());
+  IndirectBBIns->setIndex(IndirectID);
+  IndirectBBIns->insertInto(&IndirectBB, IndirectBB.getFirstInsertionPt());
+
+  const GlobalValue::GUID CalleeGUID = AssignGUIDPass::getGUID(Callee);
+
+  auto ProfileUpdater = [&](PGOCtxProfContext &Ctx) {
+    assert(Ctx.guid() == AssignGUIDPass::getGUID(Caller));
+    assert(NewCountersSize - 2 == Ctx.counters().size());
+    // Regardless what next, all the ctx-es belonging to a function must have
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snehasish wrote:

I'm not sure what's implied by "Regardless what next", either document specific concerns or drop to make it clearer?

https://github.com/llvm/llvm-project/pull/105469