[llvm] [CGData][MachineOutliner] Global Outlining (PR #90074)

[Amara Emerson via llvm-commits]

================
@@ -585,6 +644,111 @@ void MachineOutliner::emitOutlinedFunctionRemark(OutlinedFunction &OF) {
   MORE.emit(R);
 }
 
+struct MatchedEntry {
+  size_t StartIdx;
+  size_t Length;
+  size_t Count;
+};
+
+static const HashNode *followHashNode(stable_hash StableHash,
+                                      const HashNode *Current) {
+  auto I = Current->Successors.find(StableHash);
+  return (I == Current->Successors.end()) ? nullptr : I->second.get();
+}
+
+// Find all matches in the global outlined hash tree.
+// It's quadratic complexity in theory, but it's nearly linear in practice
+// since the length of outlined sequences are small within a block.
+static std::vector<MatchedEntry> getMatchedEntries(InstructionMapper &Mapper) {
+  auto &InstrList = Mapper.InstrList;
+  auto &UnsignedVec = Mapper.UnsignedVec;
+
+  std::vector<MatchedEntry> MatchedEntries;
+  std::vector<stable_hash> Sequence;
+  auto Size = UnsignedVec.size();
+
+  // Get the global outlined hash tree built from the previous run.
+  assert(cgdata::hasOutlinedHashTree());
+  const auto *RootNode = cgdata::getOutlinedHashTree()->getRoot();
+  for (size_t I = 0; I < Size; ++I) {
+    // skip the invalid mapping that represents a large negative value.
----------------
aemerson wrote:

Capitalize the first letter in comments (also the others in this function)

but also, what's this large negative value meaning?

https://github.com/llvm/llvm-project/pull/90074