make sure there is a final return in functions that return value in asm

3 files changed, 40 insertions, 1 deletions

diff --git a/tools/js-optimizer.js b/tools/js-optimizer.js
index a8753e6f..446ca723 100644
--- a/tools/js-optimizer.js
+++ b/tools/js-optimizer.js
@@ -1400,6 +1400,7 @@ function registerize(ast, asm) {
     // We also mark local variables - i.e., having a var definition
     var localVars = {};
     var hasSwitch = false; // we cannot optimize variables if there is a switch
+    var hasReturnValue = false;
     traverse(fun, function(node, type) {
       if (type == 'var') {
         node[1].forEach(function(defined) { localVars[defined[0]] = 1 });
@@ -1411,6 +1412,8 @@ function registerize(ast, asm) {
         }
       } else if (type == 'switch') {
         hasSwitch = true;
+      } else if (asm && type == 'return' && node[1]) {
+        hasReturnValue = true;
       }
     });
     vacuum(fun);
@@ -1587,6 +1590,15 @@ function registerize(ast, asm) {
         }
       }
       denormalizeAsm(fun, finalAsmData);
+      // Add a final return if one is missing. This is not strictly a register operation, but
+      // this pass traverses the entire AST anyhow so adding it here is efficient.
+      if (hasReturnValue) {
+        var stats = getStatements(fun);
+        var last = stats[stats.length-1];
+        if (last[0] != 'return') {
+          stats.push(['return', ['num', 0]]);
+        }
+      }
     }
   });
 }
diff --git a/tools/test-js-optimizer-asm-regs-output.js b/tools/test-js-optimizer-asm-regs-output.js
index d9aa5c0c..26d1d134 100644
--- a/tools/test-js-optimizer-asm-regs-output.js
+++ b/tools/test-js-optimizer-asm-regs-output.js
@@ -18,4 +18,17 @@ function _doit(i1, i2, i3) {
   STACKTOP = i1;
   return 0 | 0;
 }
+function rett() {
+  if (f()) {
+    g();
+    return 5;
+  }
+  return 0;
+}
+function ret2t() {
+  if (f()) {
+    g();
+    return;
+  }
+}
 
diff --git a/tools/test-js-optimizer-asm-regs.js b/tools/test-js-optimizer-asm-regs.js
index 6ae7f7d0..9192f32e 100644
--- a/tools/test-js-optimizer-asm-regs.js
+++ b/tools/test-js-optimizer-asm-regs.js
@@ -20,5 +20,19 @@ function _doit($x, $y$0, $y$1) {
   STACKTOP = __stackBase__;
   return 0 | 0;
 }
-// EMSCRIPTEN_GENERATED_FUNCTIONS: ["asm", "_doit"]
+function rett() {
+  if (f()) {
+    g();
+    return 5;
+  }
+  // missing final return, need to add it
+}
+function ret2t() {
+  if (f()) {
+    g();
+    return;
+  }
+  // missing final return, but no need
+}
+// EMSCRIPTEN_GENERATED_FUNCTIONS: ["asm", "_doit", "rett", "ret2t"]