From: Philip Reames <listmail@philipreames.com>
Date: Tue, 11 Jun 2019 23:21:24 +0000 (+0000)
Subject: Fix a bug in getSCEVAtScope w.r.t. non-canonical loops
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e5bf57d8b8e9a29ef24b75172b1dcccda87ecfaa;p=llvm

Fix a bug in getSCEVAtScope w.r.t. non-canonical loops

The issue is that if we have a loop with multiple predecessors outside the loop, the code was expecting to merge them and only return if equal, but instead returned the first one seen.

I have no idea if this actually tripped anywhere.  I noticed it by accident when reading the code and have no idea how to go about constructing a test case.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@363112 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index a7b7fa26238..dc2d32856cc 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -8126,9 +8126,9 @@ const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
                     break;
                   }
                 }
-                if (!MultipleInitValues && InitValue)
-                  return getSCEV(InitValue);
               }
+              if (!MultipleInitValues && InitValue)
+                return getSCEV(InitValue);
             }
             // Okay, we know how many times the containing loop executes.  If
             // this is a constant evolving PHI node, get the final value at