Enable Local CSE by default

src/IceClFlags.def

Index: src/IceClFlags.def
diff --git a/src/IceClFlags.def b/src/IceClFlags.def
index 0fabb9cf51ed1f45a3267210ec921ec5f49926c3..49cf42cf95a9475a81068972d74feadfcfe0adfd 100644
--- a/src/IceClFlags.def
+++ b/src/IceClFlags.def
@@ -140,8 +140,12 @@ struct dev_list_flag {};
              "information to stdout at the end of program execution."),        \
     cl::init(false))                                                           \
                                                                                \
-  X(EnableExperimental, bool, dev_opt_flag, "enable-experimental",             \
-    cl::desc("Enable Optimizations not yet part of O2"),                       \
+  X(LocalCSE, bool, dev_opt_flag, "lcse",                                      \

[John, 2016/07/28 14:21:50]

nit: instead of two bool flags (lcse, lcse-no-ssa), I would suggest using a
single, enum flag (e.g., -target). I would name the flag cse, and the values,
{no, yes, yes-no-assume-cse)

+    cl::desc("Local Common Subexpression elimination"),                        \
+    cl::init(true))                                                            \
+                                                                               \
+  X(LocalCSENoSSA, bool, dev_opt_flag, "lcse-no-ssa",                          \
+    cl::desc("Do not assume SSA for lcse"),                                    \
     cl::init(false))                                                           \
                                                                                \
   X(EnablePhiEdgeSplit, bool, dev_opt_flag, "phi-edge-split",                  \
@@ -184,7 +188,7 @@ struct dev_list_flag {};
     cl::init(false))                                                           \
                                                                                \
    X(LocalCseMaxIterations, int, dev_opt_flag, "lcse-max-iters",               \
-    cl::desc("Number of times local-cse is run on a block"), cl::init(2))      \
+    cl::desc("Number of times local-cse is run on a block"), cl::init(1))      \
                                                                                \
   X(LoopInvariantCodeMotion, bool, dev_opt_flag, "licm",                       \
     cl::desc("Hoist loop invariant arithmetic operations"), cl::init(false))   \