[PM] Switch the downward invalidation to be incremental where only the

one function's analyses are invalidated at a time. Also switch the
preservation of the proxy to *fully* preserve the lower (function)
analyses.

Combined, this gets both upward and downward analysis invalidation to
a point I'm happy with:

- A function pass invalidates its function analyses, and its parent's
  module analyses.
- A module pass invalidates all of its functions' analyses including the
  set of which functions are in the module.
- A function pass can preserve a module analysis pass.
- If all function passes preserve a module analysis pass, that
  preservation persists. If any doesn't the module analysis is
  invalidated.
- A module pass can opt into managing *all* function analysis
  invalidation itself or *none*.
- The conservative default is none, and the proxy takes the maximally
  conservative approach that works even if the set of functions has
  changed.
- If a module pass opts into managing function analysis invalidation it
  has to propagate the invalidation itself, the proxy just does nothing.

The only thing really missing is a way to query for a cached analysis or
nothing at all. With this, function passes can more safely request
a cached module analysis pass without fear of it accidentally running
part way through.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@195519 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 1 deletions

diff --git a/include/llvm/IR/PassManager.h b/include/llvm/IR/PassManager.h
index 6604c1851c..4d0c09234b 100644
--- a/include/llvm/IR/PassManager.h
+++ b/include/llvm/IR/PassManager.h
@@ -709,10 +709,22 @@ public:
     PreservedAnalyses PA = PreservedAnalyses::all();
     for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I) {
       PreservedAnalyses PassPA = Pass.run(I, FAM);
+
+      // We know that the function pass couldn't have invalidated any other
+      // function's analyses (that's the contract of a function pass), so
+      // directly handle the function analysis manager's invalidation here.
+      if (FAM)
+        FAM->invalidate(I, PassPA);
+
+      // Then intersect the preserved set so that invalidation of module
+      // analyses will eventually occur when the module pass completes.
       PA.intersect(llvm_move(PassPA));
     }
 
-    // By definition we preserve the proxy.
+    // By definition we preserve the proxy. This precludes *any* invalidation
+    // of function analyses by the proxy, but that's OK because we've taken
+    // care to invalidate analyses in the function analysis manager
+    // incrementally above.
     PA.preserve<FunctionAnalysisManagerModuleProxy>();
     return PA;
   }