[PH] Replace uses of AssertingVH from members of analysis results with

a lazy-asserting PoisoningVH.

AssertVH is fundamentally incompatible with cache-invalidation of
analysis results. The invaliadtion happens after the AssertingVH has
already fired. Instead, use a PoisoningVH that will assert if the
dangling handle is ever used rather than merely be assigned or
destroyed.

This patch also removes all of the (numerous) doomed attempts to work
around this fundamental incompatibility. It is a pretty significant
simplification IMO.

The most interesting change is in the Inliner where we still do some
clearing because we don't want to rely on the coarse grained
invalidation strategy of the containing pass manager. However, I prefer
the approach that contains this logic to the cleanup phase of the
Inliner, and I think we could enhance the CGSCC analysis management
layer to make this even better in the future if desired.

The rest is straight cleanup.

I've also added a test for one of the harder cases to work around: when
a *module analysis* contains many AssertingVHes pointing at functions.

Differential Revision: https://reviews.llvm.org/D29006

llvm-svn: 292928

2 files changed, 5 insertions, 5 deletions

diff --git a/llvm/test/Transforms/GlobalDCE/crash-assertingvh.ll b/llvm/test/Transforms/GlobalDCE/crash-assertingvh.ll
index 184d6ae7d8e..2919999d5e2 100644
--- a/llvm/test/Transforms/GlobalDCE/crash-assertingvh.ll
+++ b/llvm/test/Transforms/GlobalDCE/crash-assertingvh.ll
@@ -3,6 +3,7 @@
 ; to assert when global DCE deletes the body of the function.
 ;
 ; RUN: opt -disable-output < %s -passes='module(function(jump-threading),globaldce)'
+; RUN: opt -disable-output < %s -passes='module(rpo-functionattrs,globaldce)'
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
diff --git a/llvm/test/Transforms/Inline/clear-analyses.ll b/llvm/test/Transforms/Inline/clear-analyses.ll
index 1fde513f282..4b1d37ca29a 100644
--- a/llvm/test/Transforms/Inline/clear-analyses.ll
+++ b/llvm/test/Transforms/Inline/clear-analyses.ll
@@ -1,8 +1,7 @@
-; Test that the inliner clears analyses which may hold references to function
-; bodies when it decides to delete them after inlining the last caller.
-; We check this by using correlated-propagation to populate LVI with basic
-; block references that would dangle if we failed to clear the inlined function
-; body.
+; Test that when a pass like correlated-propagation populates an analysis such
+; as LVI with references back into the IR of a function that the inliner will
+; delete, this doesn't crash or go awry despite the inliner clearing the analyses
+; separately from when it deletes the function.
 ;
 ; RUN: opt -debug-pass-manager -S < %s 2>&1 \
 ; RUN:     -passes='cgscc(inline,function(correlated-propagation))' \