flip associative binaries when safe to do so for elimination purposes

3 files changed, 23 insertions, 0 deletions

diff --git a/tools/eliminator/eliminator-test-output.js b/tools/eliminator/eliminator-test-output.js
index c32266df..bff9071b 100644
--- a/tools/eliminator/eliminator-test-output.js
+++ b/tools/eliminator/eliminator-test-output.js
@@ -89,6 +89,9 @@ function b() {
   }
   var $156;
   HEAP32[$139 + ($136 << 4) + 4 >> 2] = _sqlite3FindFunction($145, $147, $148, $156, $135, 0);
+  farr();
+  f3(f1() + f2());
+  farr();
   return cheez();
 }
 function c() {
diff --git a/tools/eliminator/eliminator-test.js b/tools/eliminator/eliminator-test.js
index 1c6af7f3..d901bc78 100644
--- a/tools/eliminator/eliminator-test.js
+++ b/tools/eliminator/eliminator-test.js
@@ -109,6 +109,11 @@ function b() {
   }
   var $156;
   HEAP32[$139 + ($136 << 4) + 4 >> 2] = _sqlite3FindFunction($145, $147, $148, $156, $135, 0);
+  farr();
+  var $a = f1();
+  var $b = f2() + $a; // this could be reordered to facilitate optimization
+  f3($b);
+  farr();
   var finality = cheez();
   return finality;
 }
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index 855cf6a5..222bd0f4 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -132,6 +132,8 @@ var LOOP = set('do', 'while', 'for');
 var LOOP_FLOW = set('break', 'continue');
 var ASSIGN_OR_ALTER = set('assign', 'unary-postfix', 'unary-prefix');
 var CONTROL_FLOW = set('do', 'while', 'for', 'if', 'switch');
+var NAME_OR_NUM = set('name', 'num');
+var ASSOCIATIVE_BINARIES = set('+', '*', '|', '&', '^');
 
 var NULL_NODE = ['name', 'null'];
 var UNDEFINED_NODE = ['unary-prefix', 'void', ['num', 0]];
@@ -1635,8 +1637,21 @@ function eliminate(ast) {
             }
           }
         } else if (type == 'binary') {
+          var flipped = false;
+          if (node[1] in ASSOCIATIVE_BINARIES && !(node[2][0] in NAME_OR_NUM) && node[3][0] in NAME_OR_NUM) { // TODO recurse here?
+            // associatives like + and * can be reordered in the simple case of one of the sides being a name, since we assume they are all just numbers
+            var temp = node[2];
+            node[2] = node[3];
+            node[3] = temp;
+            flipped = true;
+          }
           traverseInOrder(node[2]);
           traverseInOrder(node[3]);
+          if (flipped && node[2][0] in NAME_OR_NUM) { // dunno if we optimized, but safe to flip back - and keeps the code closer to the original and more readable
+            var temp = node[2];
+            node[2] = node[3];
+            node[3] = temp;
+          }
         } else if (type == 'name') {
           if (!ignoreName) { // ignoreName means we are the name of something like a call or a sub - irrelevant for us
             var name = node[1];