handle empty loops in new loop optimizations; fixes #1270

3 files changed, 6 insertions, 2 deletions

diff --git a/tools/eliminator/asm-eliminator-test-output.js b/tools/eliminator/asm-eliminator-test-output.js
index 9b874ba6..a7eebe25 100644
--- a/tools/eliminator/asm-eliminator-test-output.js
+++ b/tools/eliminator/asm-eliminator-test-output.js
@@ -5047,5 +5047,6 @@ function looop7() {
     }
   }
   HEAP32[$old_0_i107_i >> 2] = HEAP32[$696 >> 2] | 0;
+  while (1) {}
 }
 
diff --git a/tools/eliminator/asm-eliminator-test.js b/tools/eliminator/asm-eliminator-test.js
index 9524bde2..22b6ddec 100644
--- a/tools/eliminator/asm-eliminator-test.js
+++ b/tools/eliminator/asm-eliminator-test.js
@@ -6771,6 +6771,9 @@ function looop7() {
     }
   }
   HEAP32[$old_0_i107_i >> 2] = HEAP32[$696 >> 2] | 0;
+  // empty loop
+  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"]
 
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index 67ce2b3d..2b05aeb3 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -2364,7 +2364,7 @@ function eliminate(ast, memSafe) {
         // try to remove loop helper variables specifically
         var stats = node[2][1];
         var last = stats[stats.length-1];
-        if (last[0] == 'if' && last[2][0] == 'block' && last[3] && last[3][0] == 'block') {
+        if (last && last[0] == 'if' && last[2][0] == 'block' && last[3] && last[3][0] == 'block') {
           var ifTrue = last[2];
           var ifFalse = last[3];
           var flip = false;
@@ -2555,7 +2555,7 @@ function asmLoopOptimizer(ast) {
         // while (1) { .. if (..) { break } } ==> do { .. } while(..)
         var stats = node[2][1];
         var last = stats[stats.length-1];
-        if (last[0] == 'if' && !last[3] && last[2][0] == 'block' && last[2][1][0][0] == 'break' && !last[2][1][0][1]) {
+        if (last && last[0] == 'if' && !last[3] && last[2][0] == 'block' && last[2][1][0][0] == 'break' && !last[2][1][0][1]) {
           var conditionToBreak = last[1];
           stats.pop();
           node[0] = 'do';