[NewPM] Fix a nasty bug with analysis invalidation in the new PM.

The issue here is that we actually allow CGSCC passes to mutate IR (and
therefore invalidate analyses) outside of the current SCC. At a minimum,
we need to support mutating parent and ancestor SCCs to support the
ArgumentPromotion pass which rewrites all calls to a function.

However, the analysis invalidation infrastructure is heavily based
around not needing to invalidate the same IR-unit at multiple levels.
With Loop passes for example, they don't invalidate other Loops. So we
need to customize how we handle CGSCC invalidation. Doing this without
gratuitously re-running analyses is even harder. I've avoided most of
these by using an out-of-band preserved set to accumulate the cross-SCC
invalidation, but it still isn't perfect in the case of re-visiting the
same SCC repeatedly *but* it coming off the worklist. Unclear how
important this use case really is, but I wanted to call it out.

Another wrinkle is that in order for this to successfully propagate to
function analyses, we have to make sure we have a proxy from the SCC to
the Function level. That requires pre-creating the necessary proxy.

The motivating test case now works cleanly and is added for
ArgumentPromotion.

Thanks for the review from Philip and Wei!

Differential Revision: https://reviews.llvm.org/D59869

llvm-svn: 357137

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/CGSCCPassManager.cpp b/llvm/lib/Analysis/CGSCCPassManager.cpp
index e811dc3a802..a0b3f83cca6 100644
--- a/llvm/lib/Analysis/CGSCCPassManager.cpp
+++ b/llvm/lib/Analysis/CGSCCPassManager.cpp
@@ -110,6 +110,12 @@ PassManager<LazyCallGraph::SCC, CGSCCAnalysisManager, LazyCallGraph &,
     // ...getContext().yield();
   }
 
+  // Before we mark all of *this* SCC's analyses as preserved below, intersect
+  // this with the cross-SCC preserved analysis set. This is used to allow
+  // CGSCC passes to mutate ancestor SCCs and still trigger proper invalidation
+  // for them.
+  UR.CrossSCCPA.intersect(PA);
+
   // Invalidation was handled after each pass in the above loop for the current
   // SCC. Therefore, the remaining analysis results in the AnalysisManager are
   // preserved. We mark this with a set so that we don't need to inspect each