fix bug with optimizeShifts asserting shifted constants can always be simplified

3 files changed, 7 insertions, 3 deletions

diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index 435a64de..9a1a408c 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -522,9 +522,11 @@ function optimizeShifts(ast) {
         if (type == 'binary' && node[1] == '>>' && node[2][0] == 'num' && node[3][0] == 'num') {
           var subNode = node[2];
           var shifts = node[3][1];
-          assert(subNode[1] % Math.pow(2, shifts) == 0, subNode);
-          subNode[1] /= Math.pow(2, shifts); // bake the shift in
-          return subNode;
+          var result = subNode[1] / Math.pow(2, shifts);
+          if (result % 1 == 0) {
+            subNode[1] = result;
+            return subNode;
+          }
         }
         // Optimize the case of ($a*80)>>2
         if (type == 'binary' && node[1] in SIMPLE_SHIFTS &&
diff --git a/tools/test-js-optimizer-t2-output.js b/tools/test-js-optimizer-t2-output.js
index bc47c9bb..30e706f9 100644
--- a/tools/test-js-optimizer-t2-output.js
+++ b/tools/test-js-optimizer-t2-output.js
@@ -73,5 +73,6 @@ function shifty($id) {
   pause(7);
   q(go());
   q(go() >> 8 << 8);
+  q(go() + 2 >> 2);
 }
 // EMSCRIPTEN_GENERATED_FUNCTIONS: ["shifty"]
diff --git a/tools/test-js-optimizer-t2.js b/tools/test-js-optimizer-t2.js
index f9b5e10c..55417ec0 100644
--- a/tools/test-js-optimizer-t2.js
+++ b/tools/test-js-optimizer-t2.js
@@ -81,5 +81,6 @@ function shifty($id) {
   pause(7);
   q(go() >> 1 << 1);
   q(go() >> 8 << 8);
+  q((go() + 2) >> 2); // the 2 >> 2 can't be simplified
 }
 // EMSCRIPTEN_GENERATED_FUNCTIONS: ["shifty"]