[llvm] [MemProf] Use radix tree for alloc contexts in bitcode summaries (PR #117066)

[Kazu Hirata via llvm-commits]

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@@ -4530,12 +4581,52 @@ void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
   Abbv = std::make_shared<BitCodeAbbrev>();
   Abbv->Add(BitCodeAbbrevOp(bitc::FS_PERMODULE_ALLOC_INFO));
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 4)); // nummib
-  // n x (alloc type, numstackids, numstackids x stackidindex)
+  // n x (alloc type, context radix tree index)
   // optional: nummib x (numcontext x total size)
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
   Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
   unsigned AllocAbbrev = Stream.EmitAbbrev(std::move(Abbv));
 
+  Abbv = std::make_shared<BitCodeAbbrev>();
+  Abbv->Add(BitCodeAbbrevOp(bitc::FS_CONTEXT_RADIX_TREE_ARRAY));
+  // n x entry
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Array));
+  Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 8));
+  unsigned RadixAbbrev = Stream.EmitAbbrev(std::move(Abbv));
+
+  // First walk through all the functions and collect the allocation contexts in
+  // their associated summaries, for use in constructing a radix tree of
+  // contexts. Note that we need to do this in the same order as the functions
+  // are processed further below since the call stack positions in the resulting
+  // radix tree array are identified based on this order.
+  MapVector<CallStackId, llvm::SmallVector<LinearFrameId>> CallStacks;
+  for (const Function &F : M) {
+    // Summary emission does not support anonymous functions, they have to
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kazutakahirata wrote:

Did you mean this?

```suggestion
    // Summary emission does not support anonymous functions, they have to be
```

https://github.com/llvm/llvm-project/pull/117066