From: Sanjoy Das <sanjoy@playingwithpointers.com>
Date: Sun, 25 Sep 2016 23:12:06 +0000 (+0000)
Subject: [SCEV] Document a gotcha; NFC
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bfa3983f1bd0d3257e49c81ad09ff33b35b8e320;p=llvm

[SCEV] Document a gotcha; NFC

We should re-consider the design decision that led to this gotcah, but
for now just document it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@282367 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h
index 64c0378ec6f..830334db691 100644
--- a/include/llvm/Analysis/ScalarEvolution.h
+++ b/include/llvm/Analysis/ScalarEvolution.h
@@ -368,6 +368,9 @@ public:
 /// This class represents a composition of other SCEV predicates, and is the
 /// class that most clients will interact with.  This is equivalent to a
 /// logical "AND" of all the predicates in the union.
+///
+/// NB! Unlike other SCEVPredicate sub-classes this class does not live in the
+/// ScalarEvolution::Preds folding set.  This is why the \c add function is sound.
 class SCEVUnionPredicate final : public SCEVPredicate {
 private:
   typedef DenseMap<const SCEV *, SmallVector<const SCEVPredicate *, 4>>