From 408b703e38a8d9aaa68fc576b105ed35ca955a71 Mon Sep 17 00:00:00 2001
From: Shinji Okumura <okuraofvegetable@gmail.com>
Date: Sun, 30 Aug 2020 03:23:41 +0900
Subject: [PATCH] [Attributor][NFC] Do not manifest noundef for positions to be
 changed to undef

This patch fixes AANoUndef manifestation.
We should not manifest noundef for positions that will be changed to undef.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D86835
---
 lib/Transforms/IPO/AttributorAttributes.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/Transforms/IPO/AttributorAttributes.cpp b/lib/Transforms/IPO/AttributorAttributes.cpp
index 8098379b659..5c4754c5738 100644
--- a/lib/Transforms/IPO/AttributorAttributes.cpp
+++ b/lib/Transforms/IPO/AttributorAttributes.cpp
@@ -7812,6 +7812,13 @@ struct AANoUndefImpl : AANoUndef {
     // values.
     if (A.isAssumedDead(getIRPosition(), nullptr, nullptr))
       return ChangeStatus::UNCHANGED;
+    // A position whose simplified value does not have any value is
+    // considered to be dead. We don't manifest noundef in such positions for
+    // the same reason above.
+    auto &ValueSimplifyAA = A.getAAFor<AAValueSimplify>(
+        *this, getIRPosition(), /* TrackDependence */ false);
+    if (!ValueSimplifyAA.getAssumedSimplifiedValue(A).hasValue())
+      return ChangeStatus::UNCHANGED;
     return AANoUndef::manifest(A);
   }
 };