From: Johannes Doerfert <jdoerfert@anl.gov>
Date: Wed, 7 Aug 2019 22:32:38 +0000 (+0000)
Subject: [Attributor][NFC] Avoid unnecessary liveness queries
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e892d1f282c0f7458353c4b3e22b7e58e873e9f0;p=llvm

[Attributor][NFC] Avoid unnecessary liveness queries

If we know everything is live there is no need to query for liveness.
Indicating a pessimistic fixpoint will cause the state to be "invalid"
which will cause the Attributor to not return the AAIsDead on request,
which will prevent us from querying isAssumedDead().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368223 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/IPO/Attributor.cpp b/lib/Transforms/IPO/Attributor.cpp
index 46dd8b447ec..2cc140a099f 100644
--- a/lib/Transforms/IPO/Attributor.cpp
+++ b/lib/Transforms/IPO/Attributor.cpp
@@ -1617,6 +1617,16 @@ ChangeStatus AAIsDeadImpl::updateImpl(Attributor &A,
       dbgs() << "[AAIsDead] AssumedLiveBlocks: " << AssumedLiveBlocks.size()
              << " Total number of blocks: " << getAnchorScope().size() << "\n");
 
+  // If we know everything is live there is no need to query for liveness.
+  if (NoReturnCalls.empty() &&
+      getAnchorScope().size() == AssumedLiveBlocks.size()) {
+    // Indicating a pessimistic fixpoint will cause the state to be "invalid"
+    // which will cause the Attributor to not return the AAIsDead on request,
+    // which will prevent us from querying isAssumedDead().
+    indicatePessimisticFixpoint();
+    assert(!isValidState() && "Expected an invalid state!");
+  }
+
   return Status;
 }