Add a TODO in SignaturePruning (#5611)

1 files changed, 8 insertions, 0 deletions

diff --git a/src/passes/SignaturePruning.cpp b/src/passes/SignaturePruning.cpp
index cd3f4abf6..dd6d278d1 100644
--- a/src/passes/SignaturePruning.cpp
+++ b/src/passes/SignaturePruning.cpp
@@ -163,6 +163,14 @@ struct SignaturePruning : public Pass {
     SubTypes subTypes(*module);
 
     // Find parameters to prune.
+    //
+    // TODO: The order matters here, and more than one cycle can find more work
+    //       in some cases, as finding a parameter is a constant and removing it
+    //       can lead to another call (that receives that parameter's value) to
+    //       now have constant parameters as well, and so it becomes
+    //       optimizable. We could do a topological sort or greatest fixed point
+    //       analysis to be optimal (that could handle a recursive call with a
+    //       constant).
     for (auto& [type, funcs] : sigFuncs) {
       auto sig = type.getSignature();
       auto& info = allInfo[type];