VM: Enable branch merging of isnan, isinf.

runtime/vm/simulator_dbc.cc

Index: runtime/vm/simulator_dbc.cc
diff --git a/runtime/vm/simulator_dbc.cc b/runtime/vm/simulator_dbc.cc
index c3998aff11a6ba832c47f211676d9cb4c8b44108..5161e57937117db1f3dbc0f446427c2a6249e802 100644
--- a/runtime/vm/simulator_dbc.cc
+++ b/runtime/vm/simulator_dbc.cc
@@ -2229,16 +2229,20 @@ RawObject* Simulator::Call(const Code& code,
   }
 
   {
-    BYTECODE(DoubleIsNaN, A_D);
-    const double v = bit_cast<double, RawObject*>(FP[rD]);
-    FP[rA] = isnan(v) ? true_value : false_value;
+    BYTECODE(DoubleIsNaN, A);
+    const double v = bit_cast<double, RawObject*>(FP[rA]);
+    if (!isnan(v)) {
+      pc++;
+    }
     DISPATCH();
   }
 
   {
-    BYTECODE(DoubleIsInfinite, A_D);
-    const double v = bit_cast<double, RawObject*>(FP[rD]);
-    FP[rA] = isinf(v) ? true_value : false_value;
+    BYTECODE(DoubleIsInfinite, A);
+    const double v = bit_cast<double, RawObject*>(FP[rA]);
+    if (!isinf(v)) {
+      pc++;
+    }
     DISPATCH();
   }