Subzero: Implemented codegen for poisoning and unpoisoning stack redzones

BUG=https://bugs.chromium.org/p/nativeclient/issues/detail?id=4374
R=kschimpf@google.com, stichnot@chromium.org

Review URL: https://codereview.chromium.org/2194853003 .
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index d55f79b..eace318 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -897,7 +897,7 @@
     uint32_t Align1 = A1->getAlignInBytes();
     uint32_t Align2 = A2->getAlignInBytes();
     if (Align1 == Align2)
-      return A1->getNumber() > A2->getNumber();
+      return A1->getNumber() < A2->getNumber();
     else
       return Align1 > Align2;
   });