Enable register unit liveness by default.

Soon we won't need to compute live intervals for physical registers.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158865 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index 153d1c3..09bf817 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -41,7 +41,7 @@
 using namespace llvm;
 
 // Temporary option to enable regunit liveness.
-static cl::opt<bool> LiveRegUnits("live-regunits", cl::Hidden);
+static cl::opt<bool> LiveRegUnits("live-regunits", cl::Hidden, cl::init(true));
 
 STATISTIC(numIntervals , "Number of original intervals");