From: Evgeniy Stepanov <eugeni.stepanov@gmail.com>
Date: Fri, 25 Jan 2013 15:35:29 +0000 (+0000)
Subject: [msan] A comment on ICmp handling logic.
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=94d1f5b10cbc65d12fc8eb46fd36a2f407cf4a35;p=oota-llvm.git

[msan] A comment on ICmp handling logic.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173453 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index 64882c284b3..a329dcc6bee 100644
--- a/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -1211,6 +1211,9 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     A = IRB.CreatePointerCast(A, Sa->getType());
     B = IRB.CreatePointerCast(B, Sb->getType());
 
+    // Let [a0, a1] be the interval of possible values of A, taking into account
+    // its undefined bits. Let [b0, b1] be the interval of possible values of B.
+    // Then (A cmp B) is defined iff (a0 cmp b1) == (a1 cmp b0).
     bool IsSigned = I.isSigned();
     Value *S1 = IRB.CreateICmp(I.getPredicate(),
                                getLowestPossibleValue(IRB, A, Sa, IsSigned),