[llvm] [DebugInfo] Handle followup loop metadata in updateLoopMetadataDebugLocations (PR #157557)

[Stephen Tozer via llvm-commits]

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@@ -375,6 +375,32 @@ bool DebugInfoFinder::addScope(DIScope *Scope) {
   return true;
 }
 
+// Recursively handle DILocations in followup metadata etc.
+static Metadata *updateLoopMetadataDebugLocationsRecursive(
+    Metadata *MetadataIn, function_ref<Metadata *(Metadata *)> Updater) {
+  const MDNode *M = dyn_cast_or_null<MDNode>(MetadataIn);
+  // The loop metadata options should start with a MDString.
+  if (!M || M->getNumOperands() < 1 || !isa<MDString>(M->getOperand(0)))
+    return nullptr;
+
+  bool Updated = false;
+  SmallVector<Metadata *, 4> MDs{M->getOperand(0)};
+  for (Metadata *MD : llvm::drop_begin(M->operands())) {
+    if (!MD) {
+      MDs.push_back(nullptr);
+    } else if (Metadata *NewMD =
+                   updateLoopMetadataDebugLocationsRecursive(MD, Updater)) {
+      MDs.push_back(NewMD);
+      Updated = true;
+    } else if (Metadata *NewMD = Updater(MD)) {
+      MDs.push_back(NewMD);
+      Updated |= NewMD != MD;
+    }
+  }
+
+  return Updated ? MDNode::get(M->getContext(), MDs) : nullptr;
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SLTozer wrote:

Is it guaranteed that there are no `distinct` loop metadata options? I can't see a reason they would exist, but may be worth adding an assert to that effect anyway.

https://github.com/llvm/llvm-project/pull/157557