Fix three bugs with handling negative zero in the optimizing compiler.

test/mjsunit/math-floor.js

Index: test/mjsunit/math-floor.js
===================================================================
--- test/mjsunit/math-floor.js	(revision 8868)
+++ test/mjsunit/math-floor.js	(working copy)
@@ -51,6 +51,17 @@
   testFloor(-Infinity, -Infinity);
   testFloor(NaN, NaN);
 
+  // Ensure that a negative zero coming from Math.floor is properly handled
+  // by other operations.
+  function ifloor(x) {
+    return 1 / Math.floor(x);
+  }
+  assertEquals(-Infinity, ifloor(-0));
+  assertEquals(-Infinity, ifloor(-0));
+  assertEquals(-Infinity, ifloor(-0));
+  %OptimizeFunctionOnNextCall(ifloor);
+  assertEquals(-Infinity, ifloor(-0));
+
   testFloor(0, 0.1);
   testFloor(0, 0.49999999999999994);
   testFloor(0, 0.5);
@@ -129,3 +140,19 @@
 for (var i = 0; i < 500; i++) {
   test();
 }
+
+
+// Regression test for a bug where a negative zero coming from Math.floor
+// was not properly handled by other operations.
+function floorsum(i, n) {
+  var ret = Math.floor(n);
+  while (--i > 0) {
+    ret += Math.floor(n);
+  }
+  return ret;
+}
+assertEquals(-0, floorsum(1, -0));
+%OptimizeFunctionOnNextCall(floorsum);
+// The optimized function will deopt.  Run it with enough iterations to try
+// to optimize via OSR (triggering the bug).
+assertEquals(-0, floorsum(100000, -0));