CodeGen: BlockPlacement: Reduce TriangleChainCount to 2

This produces a 1% speedup on an important internal Google benchmark
(protocol buffers), with no other regressions in google or in the llvm
test-suite. Only 5 targets in the entire llvm test-suite are affected,
and on those 5 targets the size increase is 0.027%

llvm-svn: 297925
diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index cba1767..d3bf95b 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -149,7 +149,7 @@
     "triangle-chain-count",
     cl::desc("Number of triangle-shaped-CFG's that need to be in a row for the "
              "triangle tail duplication heuristic to kick in. 0 to disable."),
-    cl::init(3),
+    cl::init(2),
     cl::Hidden);
 
 extern cl::opt<unsigned> StaticLikelyProb;