Check elimination: Learn from if(CompareMap(x)) on true branch.

test/mjsunit/compiler/compare_map_elim.js

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
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 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-function f(a) {
- return {className: 'xxx'};
+// Flags: --allow-natives-syntax --check-elimination
+
+a = {
+  f: function() { this.y = 3; }
+};
+b = {
+  f: function() { this.y = 4; }
 };
 
-var x = 1;
-
-function g(active) {
- for (i = 1; i <= 20000; i++) {
-   if (i == active) {
-     x = i;
-     if (f("" + i) != null) { }
-   } else {
-     if (f("" + i) != null) { }
-   }
- }
+function x(z) {
+  return z.f();
 }
 
-g(0);
+x(a);
+x(b);
+x(a);
+x(b);
+x(a);
+x(b);
+
+%OptimizeFunctionOnNextCall(x)
+
+x(a);
+x(b);