Quick: Fix and enable DCE and improve GVN/DCE cleanup.

When eliminating a move by renaming its source register,
check that it doesn't conflict with vreg usage by insns
between the defining insn and the move.

Improve the GVN/DCE cleanup so that it can handle cases
where GVN or DCE is individually disabled in the pass driver
but not in the disable_opt flags.

Bug: 19419671
Change-Id: I49bb67b81509f51fbaf90c6016c509962be43736
diff --git a/compiler/dex/quick/quick_compiler.cc b/compiler/dex/quick/quick_compiler.cc
index 39eb117..73cfe92 100644
--- a/compiler/dex/quick/quick_compiler.cc
+++ b/compiler/dex/quick/quick_compiler.cc
@@ -575,7 +575,7 @@
   // (1 << kNullCheckElimination) |
   // (1 << kClassInitCheckElimination) |
   // (1 << kGlobalValueNumbering) |
-  (1 << kGvnDeadCodeElimination) |
+  // (1 << kGvnDeadCodeElimination) |
   // (1 << kLocalValueNumbering) |
   // (1 << kPromoteRegs) |
   // (1 << kTrackLiveTemps) |