Math.* have no side effects

3 files changed, 36 insertions, 9 deletions

diff --git a/tools/eliminator/eliminator-test-output.js b/tools/eliminator/eliminator-test-output.js
index 1a6506ed..0171e99b 100644
--- a/tools/eliminator/eliminator-test-output.js
+++ b/tools/eliminator/eliminator-test-output.js
@@ -6119,4 +6119,7 @@ function intoCond() {
   HEAP32[$115 >> 2] = $NumWords;
  }
 }
+function math(a, b, c, d) {
+ print(Math_imul(d) + (Math_fround(c) + (a + Math_abs(b))));
+}
 
diff --git a/tools/eliminator/eliminator-test.js b/tools/eliminator/eliminator-test.js
index ffad69ea..ef17b388 100644
--- a/tools/eliminator/eliminator-test.js
+++ b/tools/eliminator/eliminator-test.js
@@ -8852,5 +8852,13 @@ function intoCond() {
   HEAP32[$504 >> 2] = $503;
  }
 }
-// EMSCRIPTEN_GENERATED_FUNCTIONS: ["a", "b", "c", "f", "g", "h", "py", "r", "t", "f2", "f3", "llvm3_1", "_inflate", "_malloc", "_mallocNoU", "asm", "phi", "intoCond"]
+function math(a, b, c, d) {
+ var x, y, z, w;
+ x = a;
+ y = Math_abs(b);
+ z = Math_fround(c);
+ w = Math_imul(d);
+ print(x + y + z + w);
+}
+// EMSCRIPTEN_GENERATED_FUNCTIONS: ["a", "b", "c", "f", "g", "h", "py", "r", "t", "f2", "f3", "llvm3_1", "_inflate", "_malloc", "_mallocNoU", "asm", "phi", "intoCond", "math"]
 
diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index 8b05fc38..d2bfcd91 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -1142,12 +1142,26 @@ function simplifyNotComps(ast) {
   simplifyNotCompsPass = false;
 }
 
+function callHasSideEffects(node) { // checks if the call itself (not the args) has side effects (or is not statically known)
+  return !(node[1][0] === 'name' && /^Math_/.test(node[1][1]));
+}
+
 function hasSideEffects(node) { // this is 99% incomplete!
   switch (node[0]) {
     case 'num': case 'name': case 'string': return false;
     case 'unary-prefix': return hasSideEffects(node[2]);
     case 'binary': return hasSideEffects(node[2]) || hasSideEffects(node[3]);
     case 'sub': return hasSideEffects(node[1]) || hasSideEffects(node[2]);
+    case 'call': {
+      if (callHasSideEffects(node)) return true;
+      // This is a statically known call, with no side effects. only args can side effect us
+      var args = node[2];
+      var num = args.length;
+      for (var i = 0; i < num; i++) {
+        if (hasSideEffects(args[i])) return true;
+      }
+      return false;
+    }
     default: return true;
   }
 }
@@ -2445,14 +2459,16 @@ function eliminate(ast, memSafe) {
           for (var i = 0; i < args.length; i++) {
             traverseInOrder(args[i]);
           }
-          // these two invalidations will also invalidate calls
-          if (!globalsInvalidated) {
-            invalidateGlobals();
-            globalsInvalidated = true;
-          }
-          if (!memoryInvalidated) {
-            invalidateMemory();
-            memoryInvalidated = true;
+          if (callHasSideEffects(node)) {
+            // these two invalidations will also invalidate calls
+            if (!globalsInvalidated) {
+              invalidateGlobals();
+              globalsInvalidated = true;
+            }
+            if (!memoryInvalidated) {
+              invalidateMemory();
+              memoryInvalidated = true;
+            }
           }
         } else if (type === 'if') {
           if (allowTracking) {