optimize redundant frounds in -O3

emcc

@@ -1672,6 +1672,8 @@ try:
 
       js_optimizer_queue += ['simplifyExpressions']
 
+      if opt_level >= 3 and shared.Settings.PRECISE_F32: js_optimizer_queue += ['optimizeFrounds']
+
   if closure and not shared.Settings.ASM_JS:
     flush_js_optimizer_queue()
 

tests/test_other.py

@@ -1780,7 +1780,7 @@ f.close()
       (path_from_root('tools', 'test-js-optimizer-asm-pre.js'), open(path_from_root('tools', 'test-js-optimizer-asm-pre-output.js')).read(),
        ['asm', 'simplifyExpressions']),
       (path_from_root('tools', 'test-js-optimizer-asm-pre-f32.js'), open(path_from_root('tools', 'test-js-optimizer-asm-pre-output-f32.js')).read(),
-       ['asm', 'asmPreciseF32', 'simplifyExpressions']),
+       ['asm', 'asmPreciseF32', 'simplifyExpressions', 'optimizeFrounds']),
       (path_from_root('tools', 'test-js-optimizer-asm-last.js'), open(path_from_root('tools', 'test-js-optimizer-asm-last-output.js')).read(),
        ['asm', 'last']),
       (path_from_root('tools', 'test-js-optimizer-asm-relocate.js'), open(path_from_root('tools', 'test-js-optimizer-asm-relocate-output.js')).read(),

tools/js-optimizer.js

@@ -5099,6 +5099,17 @@ function safeHeap(ast) {
   });
 }
 
+function optimizeFrounds(ast) {
+  // collapse fround(fround(..)), which can happen due to elimination
+  function fix(node) {
+    traverseChildren(node, fix);
+    if (node[0] === 'call' && node[1][0] === 'name' && node[1][1] === 'Math_fround' && node[2][0][0] === 'call' && node[2][0][1][0] === 'name' && node[2][0][1][1] === 'Math_fround') {
+      return node[2][0];
+    }
+  }
+  traverseChildren(ast, fix);
+}
+
 // Last pass utilities
 
 // Change +5 to DOT$ZERO(5). We then textually change 5 to 5.0 (uglify's ast cannot differentiate between 5 and 5.0 directly)
@@ -5210,6 +5221,7 @@ var passes = {
   relocate: relocate,
   outline: outline,
   safeHeap: safeHeap,
+  optimizeFrounds: optimizeFrounds,
 
   // flags
   minifyWhitespace: function() { minifyWhitespace = true },

tools/test-js-optimizer-asm-pre-f32.js

@@ -8,4 +8,10 @@ function badf2() {
  $9 = (HEAPF32[tempDoublePtr>>2]=$8,HEAP32[tempDoublePtr>>2]|0);
  HEAP32[$gep23_asptr>>2] = $9;
 }
-// EMSCRIPTEN_GENERATED_FUNCTIONS: ["a", "b", "rett", "ret2t", "retf", "i32_8", "tempDoublePtr", "boxx", "_main", "badf", "badf2"]
+function dupe() {
+ x = Math_fround(x);
+ x = Math_fround(Math_fround(x));
+ x = Math_fround(Math_fround(Math_fround(x)));
+ x = Math_fround(Math_fround(Math_fround(Math_fround(x))));
+}
+// EMSCRIPTEN_GENERATED_FUNCTIONS: ["badf", "badf2", "dupe"]

tools/test-js-optimizer-asm-pre-output-f32.js

@@ -8,4 +8,10 @@ function badf2() {
  $9 = Math_fround($8);
  HEAPF32[$gep23_asptr >> 2] = $9;
 }
+function dupe() {
+ x = Math_fround(x);
+ x = Math_fround(x);
+ x = Math_fround(x);
+ x = Math_fround(x);
+}