Fix Smi-based MathMinMax on x64, and reenable smi mode.

test/mjsunit/math-min-max.js

Index: test/mjsunit/math-min-max.js
diff --git a/test/mjsunit/math-min-max.js b/test/mjsunit/math-min-max.js
index e4fd313538f53270747661268a1a1d47dfbc7c39..a4d1b27c70b39a58e0a450e410cb45274e701867 100644
--- a/test/mjsunit/math-min-max.js
+++ b/test/mjsunit/math-min-max.js
@@ -177,6 +177,21 @@ function crankshaft_test_2() {
 
 run(crankshaft_test_2);
 
+var o = { a: 1, b: 2 };
+
+// Test smi-based Math.min.
+function f(o) {
+  return Math.min(o.a, o.b);
+}
+
+assertEquals(1, f(o));
+assertEquals(1, f(o));
+%OptimizeFunctionOnNextCall(f);
+assertEquals(1, f(o));
+o.a = 5;
+o.b = 4;
+assertEquals(4, f(o));
+
 // Test overriding Math.min and Math.max
 Math.min = function(a, b) { return a + b; }
 Math.max = function(a, b) { return a - b; }