1 files changed, 71 insertions, 3 deletions
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index d22de39c..bf971951 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -78,6 +78,7 @@ function traverse(node, pre, post, stack) {
     if (stack) len = stack.length;
     var result = pre(node, type, stack);
     if (result == true) return true;
+    if (typeof result == 'object') node = result; // Continue processing on this node
     if (stack && len == stack.length) stack.push(0);
   }
   for (var i = 0; i < node.length; i++) {
@@ -259,8 +260,74 @@ function removeUnneededLabelSettings(ast) {
   });
 }
 
-// Various expression simplifications
-function simplifyExpressions(ast) {
+// Various expression simplifications. Pre run before closure (where we still have metadata), Post run after.
+
+function simplifyExpressionsPre(ast) {
+  // When there is a bunch of math like (((8+5)|0)+12)|0, only the external |0 is needed, one correction is enough.
+  // At each node, ((X|0)+Y)|0 can be transformed into (X+Y): The inner corrections are not needed
+  // TODO: Is the same is true for 0xff, 0xffff?
+
+  function simplifyBitops(ast) {
+    var SAFE_BINARY_OPS = set('+', '-', '*', '/', '%', '|');
+    var ZERO = ['num', 0];
+    var rerun = true;
+    while (rerun) {
+      rerun = false;
+      traverseGenerated(ast, function(node, type, stack) {
+        if (type == 'binary' && node[1] == '|' && (jsonCompare(node[2], ZERO) || jsonCompare(node[3], ZERO))) {
+          stack.push(1); // From here on up, no need for this kind of correction, it's done at the top
+
+          // We might be able to remove this correction
+          for (var i = stack.length-2; i >= 0; i--) {
+            if (stack[i] == 1) {
+              // Great, we can eliminate
+              rerun = true;
+              return jsonCompare(node[2], ZERO) ? node[3] : node[2];
+            } else if (stack[i] == -1) {
+              break; // Too bad, we can't
+            }
+          }
+        } else if ((type == 'binary' && node[1] in SAFE_BINARY_OPS) || type == 'num' || type == 'name') {
+          stack.push(0); // This node is safe in that it does not interfere with this optimization
+        } else {
+          stack.push(-1); // This node is dangerous! Give up if you see this before you see '1'
+        }
+      }, null, []);
+    }
+  }
+
+  // The most common mathop is addition, e.g. in getelementptr done repeatedly. We can join all of those,
+  // by doing (num+num) ==> newnum, and (name+num)+num = name+newnum
+  function joinAdditions(ast) {
+    var rerun = true;
+    while (rerun) {
+      rerun = false;
+      traverseGenerated(ast, function(node, type) {
+        if (type == 'binary' && node[1] == '+') {
+          if (node[2][0] == 'num' && node[3][0] == 'num') {
+            rerun = true;
+            return ['num', node[2][1] + node[3][1]];
+          }
+          for (var i = 2; i <= 3; i++) {
+            var ii = 5-i;
+            for (var j = 2; j <= 3; j++) {
+              if (node[i][0] == 'num' && node[ii][0] == 'binary' && node[ii][1] == '+' && node[ii][j][0] == 'num') {
+                rerun = true;
+                node[ii][j][1] += node[i][1];
+                return node[ii];
+              }
+            }
+          }
+        }
+      });
+    }
+  }
+
+  simplifyBitops(ast);
+  joinAdditions(ast);
+}
+
+function simplifyExpressionsPost(ast) {
   // We often have branchings that are simplified so one end vanishes, and
   // we then get
   //   if (!(x < 5))
@@ -373,7 +440,8 @@ var passes = {
   unGlobalize: unGlobalize,
   removeAssignsToUndefined: removeAssignsToUndefined,
   //removeUnneededLabelSettings: removeUnneededLabelSettings,
-  simplifyExpressions: simplifyExpressions,
+  simplifyExpressionsPre: simplifyExpressionsPre,
+  simplifyExpressionsPost: simplifyExpressionsPost,
   loopOptimizer: loopOptimizer
 };