eliminate loop vars even if used after increment, by adding another helper (which has less overhead than the previous helper)

3 files changed, 67 insertions, 25 deletions

diff --git a/tools/eliminator/asm-eliminator-test-output.js b/tools/eliminator/asm-eliminator-test-output.js
index 9caf99d0..1a5dca55 100644
--- a/tools/eliminator/asm-eliminator-test-output.js
+++ b/tools/eliminator/asm-eliminator-test-output.js
@@ -147,27 +147,25 @@ function looop3() {
  }
 }
 function looop4() {
- var i = 0, helper = 0;
+ var i = 0, i$looptemp = 0;
  while (1) {
   do_it();
-  helper = i + 1 | 0;
-  f(i, helper);
-  if (condition()) {
-   i = helper;
-  } else {
+  i$looptemp = i;
+  i = i + 1 | 0;
+  f(i$looptemp, i);
+  if (!condition()) {
    break;
   }
  }
 }
 function looop4b() {
- var i = 0, helper = 0;
+ var i = 0, i$looptemp = 0;
  while (1) {
   do_it();
-  helper = i + 1 | 0;
-  g(helper);
-  if (condition(i)) {
-   i = helper;
-  } else {
+  i$looptemp = i;
+  i = i + 1 | 0;
+  g(i);
+  if (!condition(i$looptemp)) {
    break;
   }
  }
@@ -251,24 +249,22 @@ function multiloop($n_0, $35) {
 function multiloop2($n_0, $35) {
  $n_0 = $n_0 | 0;
  $35 = $35 | 0;
- var $p_0 = 0, $39 = 0, $41 = 0, $46 = 0;
+ var $p_0 = 0, $41 = 0, $p_0$looptemp = 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;
+  $p_0$looptemp = $p_0;
+  $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[$39 >> 1] = $p_0;
-  $46 = $n_0 - 1 | 0;
-  if (($46 | 0) == 0) {
+  HEAP16[$p_0 >> 1] = $p_0$looptemp;
+  $n_0 = $n_0 - 1 | 0;
+  if (($n_0 | 0) == 0) {
    break;
-  } else {
-   $n_0 = $46;
-   $p_0 = $39;
   }
  }
 }
@@ -901,4 +897,18 @@ function elimOneLoopVar4() {
   }
  }
 }
+function elimOneLoopVarStillUsed() {
+ var $call10 = Math_fround(0), $curri$012 = 0, $j$010 = 0, $retval$0 = 0, $j$010$looptemp = 0;
+ while (1) {
+  $j$010$looptemp = $j$010;
+  $j$010 = $j$010 + 1 | 0;
+  if ((($curri$012 | 0) % ($j$010$looptemp | 0) & -1 | 0) == 0) {
+   break;
+  }
+  if (!(Math_fround($j$010 | 0) < $call10)) {
+   break;
+  }
+ }
+ return $retval$0 | 0;
+}
 
diff --git a/tools/eliminator/asm-eliminator-test.js b/tools/eliminator/asm-eliminator-test.js
index a3de3d9d..d5bbd8d5 100644
--- a/tools/eliminator/asm-eliminator-test.js
+++ b/tools/eliminator/asm-eliminator-test.js
@@ -1131,5 +1131,26 @@ function elimOneLoopVar4() {
   }
  }
 }
-// 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", "looop8", "multiloop", "multiloop2", "tempDouble2", "watIf", "select2", "binary", "cute", "selfAssign", "elimOneLoopVar", "elimOneLoopVar2", "elimOneLoopVar3", "elimOneLoopVar4"]
+function elimOneLoopVarStillUsed() {
+ var $0 = 0, $1 = 0, $arg$0 = 0, $arrayidx = 0, $call10 = Math_fround(0), $cmp = 0, $cmp11 = 0, $cmp119 = 0, $cmp12 = 0, $cmp7 = 0, $conv = 0, $conv8 = Math_fround(0), $conv9 = Math_fround(0), $curri$012 = 0, $inc = 0, $inc14$primes$0 = 0, $inc16 = 0, $j$010 = 0, $ok$0 = 0;
+ var $primes$011 = 0, $rem = 0, $retval$0 = 0, $sub = 0, $vararg_buffer1 = 0, label = 0, sp = 0;
+ while (1) {
+  $rem = ($curri$012 | 0) % ($j$010 | 0) & -1;
+  $cmp12 = ($rem | 0) == 0;
+  $inc = $j$010 + 1 | 0;
+  if ($cmp12) {
+   $ok$0 = 0;
+   break;
+  }
+  $conv8 = Math_fround($inc | 0);
+  $cmp11 = $conv8 < $call10;
+  if ($cmp11) {
+   $j$010 = $inc;
+  } else {
+   break;
+  }
+ }
+ return $retval$0 | 0;
+}
+// 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", "looop8", "multiloop", "multiloop2", "tempDouble2", "watIf", "select2", "binary", "cute", "selfAssign", "elimOneLoopVar", "elimOneLoopVar2", "elimOneLoopVar3", "elimOneLoopVar4", "elimOneLoopVarStillUsed"]
 
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index c4585b84..32c26c51 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -3519,12 +3519,15 @@ function eliminate(ast, memSafe) {
           seenUses[name]++;
         }
       } else if (type === 'while') {
+        if (!asm) return;
         // try to remove loop helper variables specifically
         var stats = node[2][1];
         var last = stats[stats.length-1];
         if (last && last[0] === 'if' && last[2][0] === 'block' && last[3] && last[3][0] === 'block') {
           var ifTrue = last[2];
           var ifFalse = last[3];
+          clearEmptyNodes(ifTrue[1]);
+          clearEmptyNodes(ifFalse[1]);
           var flip = false;
           if (ifFalse[1][0] && ifFalse[1][0][0] === 'break') { // canonicalize break in the if
             var temp = ifFalse;
@@ -3589,17 +3592,25 @@ function eliminate(ast, memSafe) {
                 }
               }
               if (found < 0) return;
+              // if a loop variable is used after we assigned to the helper, we must save its value and use that.
+              // (note that this can happen due to elimination, if we eliminate an expression containing the
+              // loop var far down, past the assignment!)
+              var temp = looper + '$looptemp';
               var looperUsed = false;
-              for (var i = found+1; i < stats.length && !looperUsed; i++) {
+              assert(!(temp in asmData.vars)); 
+              for (var i = found+1; i < stats.length; 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) {
+                    node[1] = temp;
                     looperUsed = true;
-                    return true;
                   }
                 });
               }
-              if (looperUsed) return;
+              if (looperUsed) {
+                asmData.vars[temp] = asmData.vars[looper];
+                stats.splice(found, 0, ['stat', ['assign', true, ['name', temp], ['name', looper]]]);
+              }
             }
             for (var l = 0; l < helpers.length; l++) {
               for (var k = 0; k < helpers.length; k++) {