[PM] Try to improve the comments here to make what's going on more

clear.

Based on post-commit review suggestion from Sean. (Thanks!)

llvm-svn: 290488

1 files changed, 5 insertions, 3 deletions

diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
index b7609c994cf..221ee15a78e 100644
--- a/llvm/lib/Passes/PassBuilder.cpp
+++ b/llvm/lib/Passes/PassBuilder.cpp
@@ -561,10 +561,12 @@ AAManager PassBuilder::buildDefaultAAPipeline() {
   AA.registerFunctionAnalysis<TypeBasedAA>();
 
   // Add support for querying global aliasing information when available.
-  // Because this is a module analysis this will use any cached analysis state
-  // available but isn't enough to cause it to be available.
-  // FIXME: Enable once the invalidation logic supports this.
+  // Because the `AAManager` is a function analysis and `GlobalsAA` is a module
+  // analysis, all that the `AAManager` can do is query for any *cached*
+  // results from `GlobalsAA` through a readonly proxy..
 #if 0
+  // FIXME: Enable once the invalidation logic supports this. Currently, the
+  // `AAManager` will hold stale references to the module analyses.
   AA.registerModuleAnalysis<GlobalsAA>();
 #endif