For trigonometric functions call to C-libraries: they are faster than x87 operations (3% on Box2D).

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
===================================================================
--- runtime/vm/intermediate_language.cc	(revision 27253)
+++ runtime/vm/intermediate_language.cc	(working copy)
@@ -2641,6 +2641,27 @@
 }
 
 
+extern const RuntimeEntry kCosRuntimeEntry(
+    "libc_cos", reinterpret_cast<RuntimeFunction>(
+        static_cast<UnaryMathCFunction>(&cos)), 1, true, true);
+
+extern const RuntimeEntry kSinRuntimeEntry(
+    "libc_sin", reinterpret_cast<RuntimeFunction>(
+        static_cast<UnaryMathCFunction>(&sin)), 1, true, true);
+
+
+const RuntimeEntry& MathUnaryInstr::TargetFunction() const {
+  switch (kind()) {
+    case MethodRecognizer::kMathSin:
+      return kSinRuntimeEntry;
+    case MethodRecognizer::kMathCos:
+      return kCosRuntimeEntry;
+    default:
+      UNREACHABLE();
+  }
+  return kSinRuntimeEntry;
+}
+
 #undef __
 
 }  // namespace dart