Implement global load elimination based on flow engine.

test/mjsunit/compiler/load-elimination-global.js

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 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 // Flags: --allow-natives-syntax --load-elimination
 
-// Test local load elimination of redundant loads and stores.
+// Test global load elimination of redundant loads and stores.
+
+var X = true;  // For forcing branches.
+X = false;
+X = true;
+X = false;
 
 function B(x, y) {
   this.x = x;
   this.y = y;
   return this;
 }
 
 function test_load() {
   var a = new B(1, 2);
-  return a.x + a.x + a.x + a.x;
+  var f = a.x + a.x;
+  if (false) ;
+  return f + a.x + a.x;
+}
+
+function test_load2() {
+  var a = new B(1, 2);
+  var f = a.x + a.x;
+  if (true) ;
+  return f + a.x + a.x;
 }
 
 function test_store_load() {
   var a = new B(1, 2);
   a.x = 4;
-  var f = a.x;
-  a.x = 5;
-  var g = a.x;
-  a.x = 6;
-  var h = a.x;
-  a.x = 7;
-  return f + g + h + a.x;
+  var b = X ? a.x : a.x;
+  return b + a.x;
+}
+
+function test_store_load2() {
+  var a = new B(1, 2);
+  var c = 6;
+  if (X) a.x = c;
+  else a.x = c;
+  return a.x + a.x;
 }
 
 function test_nonaliasing_store1() {
   var a = new B(2, 3), b = new B(3, 4);
+  if (X) ;
   b.x = 4;
+  if (X) ;
   var f = a.x;
+  if (X) ;
   b.x = 5;
+  if (X) ;
   var g = a.x;
+  if (X) ;
   b.x = 6;
+  if (X) ;
   var h = a.x;
+  if (X) ;
   b.x = 7;
+  if (X) ;
   return f + g + h + a.x;
 }
 
+function test_loop(x) {

[mvstanton, 2013/10/17 10:32:55]

Could you have another test (or extend this one) to use a nested loop so the
recursive part of the flow engine on loop effects is exercised to some level?

+  var a = new B(2, 3);
+  var v = a.x;
+  var total = v;
+  var i = 0;
+  while (i++ < 10) {
+    total = a.x;
+    a.y = 4;
+  }
+  return total;
+}
+
 function killall() {
   try { } catch(e) { }
 }
 
 %NeverOptimizeFunction(killall);
 
 function test_store_load_kill() {
   var a = new B(1, 2);
+  if (X) ;
   a.x = 4;
+  if (X) ;
   var f = a.x;
+  if (X) ;
   a.x = 5;
+  if (X) ;
   var g = a.x;
+  if (X) ;
   killall();
+  if (X) ;
   a.x = 6;
+  if (X) ;
   var h = a.x;
+  if (X) ;
   a.x = 7;
+  if (X) ;
   return f + g + h + a.x;
 }
 
 function test_store_store() {
   var a = new B(6, 7);
+  if (X) ;
   a.x = 7;
+  if (X) ;
   a.x = 7;
+  if (X) ;
   a.x = 7;
+  if (X) ;
   a.x = 7;
+  if (X) ;
   return a.x;
 }
 
 function test(x, f) {
+  X = true;
   assertEquals(x, f());
   assertEquals(x, f());
+  X = false;
+  assertEquals(x, f());
+  assertEquals(x, f());
+  X = true;
   %OptimizeFunctionOnNextCall(f);
   assertEquals(x, f());
+  assertEquals(x, f());
+  X = false;
+  assertEquals(x, f());
+  assertEquals(x, f());
 }
 
 test(4, test_load);
-test(22, test_store_load);
+test(8, test_store_load);
+test(12, test_store_load2);
 test(8, test_nonaliasing_store1);
 test(22, test_store_load_kill);
 test(7, test_store_store);
+test(2, test_loop);