[llvm] [Inliner] Put inline history into IR as !inline_history metadata (PR #190092)

[Nikita Popov via llvm-commits]

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@@ -3269,6 +3240,33 @@ void llvm::InlineFunctionImpl(CallBase &CB, InlineFunctionInfo &IFI,
             IFI.InlinedCallSites.push_back(CB);
   }
 
+  for (CallBase *ICB : IFI.InlinedCallSites) {
+    // We only track inline history if requested, or if the inlined call site
+    // was originally an indirect call (it may have become a direct call
+    // during inlining).
+    if (TrackInlineHistory ||
+        InlinedFunctionInfo.OriginallyIndirectCalls.contains(ICB)) {
+      // !inline_history is {Callee, CB.inline_history, ICB.inline_history}.
+      SmallVector<Metadata *, 4> History;
+      History.push_back(ValueAsMetadata::get(CalledFunc));
+      if (MDNode *CBHistory = CB.getMetadata(LLVMContext::MD_inline_history)) {
+        for (const auto &Op : CBHistory->operands()) {
+          if (Op)
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nikic wrote:

Can Op really be null here?

https://github.com/llvm/llvm-project/pull/190092