Convert diamond shaped control flow into a single conditional instruction.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
diff --git a/runtime/vm/intermediate_language.cc b/runtime/vm/intermediate_language.cc
index 292d6aaf0ed60460eeddbbff82f3a1d36ab2a8f6..3bf99bd6052bce7e781d0cd08bf4cb879c711db8 100644
--- a/runtime/vm/intermediate_language.cc
+++ b/runtime/vm/intermediate_language.cc
@@ -2039,6 +2039,14 @@ void LoadIndexedInstr::InferRange() {
 }
 
 
+void IfThenElseInstr::InferRange() {
+  const intptr_t min = Utils::Minimum(if_true_, if_false_);
+  const intptr_t max = Utils::Maximum(if_true_, if_false_);
+  range_ = new Range(RangeBoundary::FromConstant(min),
+                     RangeBoundary::FromConstant(max));
+}
+
+
 void PhiInstr::InferRange() {
   RangeBoundary new_min;
   RangeBoundary new_max;