Dissociate uses with environment uses.

They are most of the times in the way when iterating. They
also complicate the logic of (future) back edge uses.

Change-Id: I152595d9913073fe901b267ca623fa0fe7432484
diff --git a/compiler/optimizing/ssa_liveness_analysis.cc b/compiler/optimizing/ssa_liveness_analysis.cc
index ea0e7c3..b674f74 100644
--- a/compiler/optimizing/ssa_liveness_analysis.cc
+++ b/compiler/optimizing/ssa_liveness_analysis.cc
@@ -341,7 +341,7 @@
   size_t end = GetEnd();
   while (use != nullptr && use->GetPosition() <= end) {
     size_t use_position = use->GetPosition();
-    if (use_position >= start && !use->GetIsEnvironment()) {
+    if (use_position >= start) {
       HInstruction* user = use->GetUser();
       size_t input_index = use->GetInputIndex();
       if (user->IsPhi()) {