optimize multiple loop variables together

3 files changed, 153 insertions, 45 deletions

diff --git a/tools/eliminator/asm-eliminator-test-output.js b/tools/eliminator/asm-eliminator-test-output.js
index a7eebe25..52c91ce1 100644
--- a/tools/eliminator/asm-eliminator-test-output.js
+++ b/tools/eliminator/asm-eliminator-test-output.js
@@ -5049,4 +5049,49 @@ function looop7() {
   HEAP32[$old_0_i107_i >> 2] = HEAP32[$696 >> 2] | 0;
   while (1) {}
 }
+function multiloop($n_0, $35) {
+  $n_0 = $n_0 | 0;
+  $35 = $35 | 0;
+  var $p_0 = 0, $41 = 0;
+  $n_0 = $35;
+  $p_0 = (HEAP32[$15 >> 2] | 0) + ($35 << 1) | 0;
+  while (1) {
+    $p_0 = $p_0 - 2 | 0;
+    $41 = HEAPU16[$p_0 >> 1] | 0;
+    if ($41 >>> 0 < $2 >>> 0) {
+      $_off0 = 0;
+    } else {
+      $_off0 = $41 - $2 & 65535;
+    }
+    HEAP16[$p_0 >> 1] = $_off0;
+    $n_0 = $n_0 - 1 | 0;
+    if (($n_0 | 0) == 0) {
+      break;
+    }
+  }
+}
+function multiloop2($n_0, $35) {
+  $n_0 = $n_0 | 0;
+  $35 = $35 | 0;
+  var $p_0 = 0, $39 = 0, $41 = 0, $46 = 0;
+  $n_0 = $35;
+  $p_0 = (HEAP32[$15 >> 2] | 0) + ($35 << 1) | 0;
+  while (1) {
+    $39 = $p_0 - 2 | 0;
+    $41 = HEAPU16[$39 >> 1] | 0;
+    if ($41 >>> 0 < $2 >>> 0) {
+      $_off0 = 0;
+    } else {
+      $_off0 = $41 - $2 & 65535;
+    }
+    HEAP16[$39 >> 1] = $p_0;
+    $46 = $n_0 - 1 | 0;
+    if (($46 | 0) == 0) {
+      break;
+    } else {
+      $n_0 = $46;
+      $p_0 = $39;
+    }
+  }
+}
 
diff --git a/tools/eliminator/asm-eliminator-test.js b/tools/eliminator/asm-eliminator-test.js
index 22b6ddec..e01a89ea 100644
--- a/tools/eliminator/asm-eliminator-test.js
+++ b/tools/eliminator/asm-eliminator-test.js
@@ -6775,5 +6775,53 @@ function looop7() {
   while (1) {
   }
 }
-// EMSCRIPTEN_GENERATED_FUNCTIONS: ["asm", "__Z11printResultPiS_j", "_segment_holding", "__ZN5identC2EiPKcPci", "_vec2Length", "exc", "label", "confuusion", "tempDouble", "_org_apache_harmony_luni_util_NumberConverter_freeFormat__", "__ZN23b2EdgeAndPolygonContact8EvaluateEP10b2ManifoldRK11b2TransformS4_", "_java_nio_charset_Charset_forNameInternal___java_lang_String", "looop2", "looop3", "looop4", "looop5", "looop6", "looop7"]
+function multiloop($n_0, $35) {
+  $n_0 = $n_0 | 0;
+  $35 = $35 | 0;
+  var $p_0 = 0, $39 = 0, $41 = 0, $46 = 0;
+  $n_0 = $35;
+  $p_0 = (HEAP32[$15 >> 2] | 0) + ($35 << 1) | 0;
+  while (1) {
+    $39 = $p_0 - 2 | 0;
+    $41 = HEAPU16[$39 >> 1] | 0;
+    if ($41 >>> 0 < $2 >>> 0) {
+      $_off0 = 0;
+    } else {
+      $_off0 = $41 - $2 & 65535;
+    }
+    HEAP16[$39 >> 1] = $_off0;
+    $46 = $n_0 - 1 | 0;
+    if (($46 | 0) == 0) {
+      break;
+    } else {
+      $n_0 = $46;
+      $p_0 = $39;
+    }
+  }
+}
+function multiloop2($n_0, $35) {
+  $n_0 = $n_0 | 0;
+  $35 = $35 | 0;
+  var $p_0 = 0, $39 = 0, $41 = 0, $46 = 0;
+  $n_0 = $35;
+  $p_0 = (HEAP32[$15 >> 2] | 0) + ($35 << 1) | 0;
+  while (1) {
+    $39 = $p_0 - 2 | 0;
+    $41 = HEAPU16[$39 >> 1] | 0;
+    if ($41 >>> 0 < $2 >>> 0) {
+      $_off0 = 0;
+    } else {
+      $_off0 = $41 - $2 & 65535;
+    }
+    HEAP16[$39 >> 1] = $p_0; // cannot optimize one, so none
+    $46 = $n_0 - 1 | 0;
+    if (($46 | 0) == 0) {
+      break;
+    } else {
+      $n_0 = $46;
+      $p_0 = $39;
+    }
+  }
+}
+// EMSCRIPTEN_GENERATED_FUNCTIONS: ["asm", "__Z11printResultPiS_j", "_segment_holding", "__ZN5identC2EiPKcPci", "_vec2Length", "exc", "label", "confuusion", "tempDouble", "_org_apache_harmony_luni_util_NumberConverter_freeFormat__", "__ZN23b2EdgeAndPolygonContact8EvaluateEP10b2ManifoldRK11b2TransformS4_", "_java_nio_charset_Charset_forNameInternal___java_lang_String", "looop2", "looop3", "looop4", "looop5", "looop6", "looop7", "multiloop", "multiloop2"]
 
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index 2b05aeb3..8e815100 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -2374,57 +2374,72 @@ function eliminate(ast, memSafe) {
             ifTrue = temp;
             flip = true;
           }
-          if (ifTrue[1][0][0] == 'break' && !ifTrue[1][1] && ifFalse[1].length == 1 && ifFalse[1][0][0] == 'stat' && ifFalse[1][0][1][0] == 'assign') {
-            var assign = ifFalse[1][0][1];
-            if (assign[1] === true && assign[2][0] == 'name' && assign[3][0] == 'name') {
-              var looper = assign[2][1];
-              var helper = assign[3][1];
-              if (definitions[helper] == 1 && seenUses[looper] == namings[looper] &&
-                  !helperReplacements[helper] && !helperReplacements[looper]) {
-                // the remaining issue is whether looper is used after the assignment to helper and before the last line (where we assign to it)
-                var found = -1;
-                for (var i = stats.length-2; i >= 0; i--) {
-                  var curr = stats[i];
-                  if (curr[0] == 'stat' && curr[1][0] == 'assign') {
-                    var currAssign = curr[1];
-                    if (currAssign[1] === true && currAssign[2][0] == 'name') {
-                      var to = currAssign[2][1];
-                      if (to == helper) {
-                        found = i;
-                        break;
-                      }
-                    }
+          if (ifTrue[1][0][0] == 'break' && !ifTrue[1][1]) {
+            var assigns = ifFalse[1];
+            var loopers = [], helpers = [];
+            for (var i = 0; i < assigns.length; i++) {
+              if (assigns[i][0] == 'stat' && assigns[i][1][0] == 'assign') {
+                var assign = assigns[i][1];
+                if (assign[1] === true && assign[2][0] == 'name' && assign[3][0] == 'name') {
+                  var looper = assign[2][1];
+                  var helper = assign[3][1];
+                  if (definitions[helper] == 1 && seenUses[looper] == namings[looper] &&
+                      !helperReplacements[helper] && !helperReplacements[looper]) {
+                    loopers.push(looper);
+                    helpers.push(helper);
                   }
                 }
-                if (found >= 0) {
-                  var looperUsed = false;
-                  for (var i = found+1; i < stats.length && !looperUsed; i++) {
-                    var curr = i < stats.length-1 ? stats[i] : last[1]; // on the last line, just look in the condition
-                    traverse(curr, function(node, type) {
-                      if (type == 'name' && node[1] == looper) {
-                        looperUsed = true;
-                        return true;
-                      }
-                    });
-                  }
-                  if (!looperUsed) {
-                    // hurrah! this is safe to do
-                    varsToRemove[helper] = 2;
-                    traverse(node, function(node, type) { // replace all appearances of helper with looper
-                      if (type == 'name' && node[1] == helper) node[1] = looper;
-                    });
-                    helperReplacements[helper] = looper; // replace all future appearances of helper with looper
-                    helperReplacements[looper] = looper; // avoid any further attempts to optimize looper in this manner (seenUses is wrong anyhow, too)
-                    // simplify the if. we remove the if branch, leaving only the else
-                    if (flip) {
-                      last[1] = simplifyNotComps(['unary-prefix', '!', last[1]]);
-                      last[2] = last[3];
+              }
+            }
+            if (loopers.length < assigns.length) return; // TODO: handle the case where can can just eliminate one. (we can't optimize the break, but we can remove the var at least)
+            for (var l = 0; l < loopers.length; l++) {
+              var looper = loopers[l];
+              var helper = helpers[l];
+              // the remaining issue is whether loopers are used after the assignment to helper and before the last line (where we assign to it)
+              var found = -1;
+              for (var i = stats.length-2; i >= 0; i--) {
+                var curr = stats[i];
+                if (curr[0] == 'stat' && curr[1][0] == 'assign') {
+                  var currAssign = curr[1];
+                  if (currAssign[1] === true && currAssign[2][0] == 'name') {
+                    var to = currAssign[2][1];
+                    if (to == helper) {
+                      found = i;
+                      break;
                     }
-                    last.pop();
                   }
                 }
               }
+              if (found < 0) return;
+              var looperUsed = false;
+              for (var i = found+1; i < stats.length && !looperUsed; i++) {
+                var curr = i < stats.length-1 ? stats[i] : last[1]; // on the last line, just look in the condition
+                traverse(curr, function(node, type) {
+                  if (type == 'name' && node[1] == looper) {
+                    looperUsed = true;
+                    return true;
+                  }
+                });
+              }
+              if (looperUsed) return;
+            }
+            // hurrah! this is safe to do
+            for (var l = 0; l < loopers.length; l++) {
+              var looper = loopers[l];
+              var helper = helpers[l];
+              varsToRemove[helper] = 2;
+              traverse(node, function(node, type) { // replace all appearances of helper with looper
+                if (type == 'name' && node[1] == helper) node[1] = looper;
+              });
+              helperReplacements[helper] = looper; // replace all future appearances of helper with looper
+              helperReplacements[looper] = looper; // avoid any further attempts to optimize looper in this manner (seenUses is wrong anyhow, too)
+            }
+            // simplify the if. we remove the if branch, leaving only the else
+            if (flip) {
+              last[1] = simplifyNotComps(['unary-prefix', '!', last[1]]);
+              last[2] = last[3];
             }
+            last.pop();
           }
         }
       }