Index: lib/CodeGen/MachineCombiner.cpp
===================================================================
--- lib/CodeGen/MachineCombiner.cpp
+++ lib/CodeGen/MachineCombiner.cpp
@@ -407,8 +407,11 @@
 /// \returns true when new instruction sequence should be generated
 /// independent if it lengthens critical path or not
 bool MachineCombiner::doSubstitute(unsigned NewSize, unsigned OldSize) {
-  if (OptSize && (NewSize < OldSize))
-    return true;
+  if (OptSize) { // First of all check OptSize option
+    if (NewSize < OldSize)
+      return true; // Do substitute in any case if new size < old size
+    return false;  // We should not do substitute if new size >= old size
+  }
   if (!TSchedModel.hasInstrSchedModelOrItineraries())
     return true;
   return false;
@@ -588,7 +591,7 @@
         // Eagerly stop after the first pattern fires.
         Changed = true;
         break;
-      } else {
+      } else if (!(OptSize && (NewInstCount > OldInstCount))) {
         // For big basic blocks, we only compute the full trace the first time
         // we hit this. We do not invalidate the trace, but instead update the
         // instruction depths incrementally.