eliminate into one-time do-while loops

4 files changed, 36 insertions, 4 deletions

diff --git a/src/utility.js b/src/utility.js
index 42e8ede4..5019e117 100644
--- a/src/utility.js
+++ b/src/utility.js
@@ -108,6 +108,12 @@ function zeros(size) {
   return ret;
 }
 
+function spaces(size) {
+  var ret = '';
+  for (var i = 0; i < size; i++) ret += ' ';
+  return ret;
+}
+
 function keys(x) {
   var ret = [];
   for (var a in x) ret.push(a);
diff --git a/tools/eliminator/eliminator-test-output.js b/tools/eliminator/eliminator-test-output.js
index fbecbf73..f0fe3f68 100644
--- a/tools/eliminator/eliminator-test-output.js
+++ b/tools/eliminator/eliminator-test-output.js
@@ -70,6 +70,14 @@ function a($directory) {
   }
   var $26 = __ZL3minIiET_S0_S0_12(4096, 4096 - $16 | 0);
   print(FUNCTION_TABLE[$22]($18, $16 + ($this + 27) | 0, $26));
+  chak();
+  do {
+    print(10);
+  } while (0);
+  var zzz1 = 10;
+  do {
+    print(zzz1);
+  } while (1);
 }
 function b() {
   var $148 = _sqlite3Strlen30($147);
diff --git a/tools/eliminator/eliminator-test.js b/tools/eliminator/eliminator-test.js
index 8a7f3d72..c968d4d7 100644
--- a/tools/eliminator/eliminator-test.js
+++ b/tools/eliminator/eliminator-test.js
@@ -89,6 +89,15 @@ function a($directory) {
   var $26 = __ZL3minIiET_S0_S0_12(4096, 4096 - $16 | 0); // cannot eliminate this because the call might modify FUNCTION_TABLE
   var $27 = FUNCTION_TABLE[$22]($18, $this + ($16 + 27) | 0, $26);
   print($27);
+  chak();
+  var zzz = 10;
+  do {
+    print(zzz);
+  } while (0);
+  var zzz1 = 10;
+  do {
+    print(zzz1);
+  } while (1); // cannot eliminate a do-while that is not one-time
 }
 function b() {
   var $148 = _sqlite3Strlen30($147);
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index b9a0bce8..b65617e1 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -1366,7 +1366,7 @@ function registerize(ast) {
   });
 }
 
-var ELIMINATION_SAFE_NODES = set('var', 'assign', 'call', 'if', 'toplevel');
+var ELIMINATION_SAFE_NODES = set('var', 'assign', 'call', 'if', 'toplevel', 'do'); // do is checked carefully, however
 var NODES_WITHOUT_ELIMINATION_SIDE_EFFECTS = set('name', 'num', 'string', 'binary', 'sub', 'unary-prefix');
 var IGNORABLE_ELIMINATOR_SCAN_NODES = set('num', 'toplevel', 'string', 'break', 'continue', 'dot', 'return'); // dot can only be STRING_TABLE.*
 var ABORTING_ELIMINATOR_SCAN_NODES = set('new', 'object', 'function', 'defun', 'switch', 'for', 'while', 'array', 'throw'); // we could handle some of these, TODO, but nontrivial (e.g. for while, the condition is hit multiple times after the body)
@@ -1550,9 +1550,11 @@ function eliminate(ast) {
       //printErr('scan: ' + JSON.stringify(node).substr(0, 50) + ' : ' + keys(tracked));
       var abort = false;
       var allowTracking = true; // false inside an if; also prevents recursing in an if
+      //var nesting = 1; // printErr-related
       function traverseInOrder(node, ignoreSub, ignoreName) {
         if (abort) return;
-        //printErr('  trav: ' + JSON.stringify(node).substr(0, 50) + ' : ' + keys(tracked));
+        //nesting++; // printErr-related
+        //printErr(spaces(2*(nesting+1)) + 'trav: ' + JSON.stringify(node).substr(0, 50) + ' : ' + keys(tracked) + ' : ' + [allowTracking, ignoreSub, ignoreName]);
         var type = node[0];
         if (type == 'assign') {
           var target = node[2];
@@ -1658,8 +1660,12 @@ function eliminate(ast) {
           traverseInOrder(node[1]);
           traverseInOrder(node[2]);
         } else if (type == 'do') {
-          traverseInOrder(node[1]);
-          if (node[2]) traverseInOrder(node[2]);
+          if (node[1][0] == 'num' && node[1][1] == 0) { // one-time loop
+            traverseInOrder(node[2]);
+          } else {
+            tracked = {};
+            abort = true;
+          }
         } else if (type == 'conditional') {
           traverseInOrder(node[1]);
           traverseInOrder(node[2]);
@@ -1671,6 +1677,7 @@ function eliminate(ast) {
           tracked = {};
           abort = true;
         }
+        //nesting--; // printErr-related
       }
       traverseInOrder(node);
     }
@@ -1705,8 +1712,10 @@ function eliminate(ast) {
       var stats = getStatements(block);
       if (!stats) return;
       tracked = {};
+      //printErr('new StatBlock');
       for (var i = 0; i < stats.length; i++) {
         var node = stats[i];
+        //printErr('StatBlock[' + i + '] => ' + JSON.stringify(node));
         var type = node[0];
         if (type == 'stat') {
           node = node[1];