diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
index b2713da..c235fd2 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyTargetMachine.cpp
@@ -301,8 +301,10 @@
   addPass(createWebAssemblyFixIrreducibleControlFlow());
 
   // Do various transformations for exception handling.
+  // Every CFG-changing optimizations should come before this.
   addPass(createWebAssemblyLateEHPrepare());
 
+  // Preparations and optimizations related to register stackification.
   if (getOptLevel() != CodeGenOpt::None) {
     // LiveIntervals isn't commonly run this late. Re-establish preconditions.
     addPass(createWebAssemblyPrepareForLiveIntervals());