EM_ASM_INT and EM_ASM_DOUBLE, which allow input and output values from EM_ASM; fixes #1819

4 files changed, 62 insertions, 12 deletions

diff --git a/src/library.js b/src/library.js
index 9db99c6c..066a060f 100644
--- a/src/library.js
+++ b/src/library.js
@@ -8676,12 +8676,19 @@ LibraryManager.library = {
   },
 
   emscripten_asm_const: function(code) {
-    // code is a constant string on the heap, so we can cache these
-    if (!Runtime.asmConstCache) Runtime.asmConstCache = {};
-    var func = Runtime.asmConstCache[code];
-    if (func) return func();
-    func = Runtime.asmConstCache[code] = eval('(function(){ ' + Pointer_stringify(code) + ' })'); // new Function does not allow upvars in node
-    return func();
+    Runtime.getAsmConst(code, 0)();
+  },
+
+  emscripten_asm_const_int__jsargs: true,
+  emscripten_asm_const_int: function(code) {
+    var args = Array.prototype.slice.call(arguments, 1);
+    return Runtime.getAsmConst(code, args.length).apply(null, args) | 0;
+  },
+
+  emscripten_asm_const_double__jsargs: true,
+  emscripten_asm_const_double: function(code) {
+    var args = Array.prototype.slice.call(arguments, 1);
+    return +Runtime.getAsmConst(code, args.length).apply(null, args);
   },
 
   emscripten_get_now: function() {
diff --git a/src/runtime.js b/src/runtime.js
index 786ae021..dedaf5ea 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -381,6 +381,18 @@ var Runtime = {
 #endif
   },
 
+  getAsmConst: function(code, numArgs) {
+    // code is a constant string on the heap, so we can cache these
+    if (!Runtime.asmConstCache) Runtime.asmConstCache = {};
+    var func = Runtime.asmConstCache[code];
+    if (func) return func;
+    var args = [];
+    for (var i = 0; i < numArgs; i++) {
+      args.push(String.fromCharCode(36) + i); // $0, $1 etc
+    }
+    return Runtime.asmConstCache[code] = eval('(function(' + args.join(',') + '){ ' + Pointer_stringify(code) + ' })'); // new Function does not allow upvars in node
+  },
+
   warnOnce: function(text) {
     if (!Runtime.warnOnce.shown) Runtime.warnOnce.shown = {};
     if (!Runtime.warnOnce.shown[text]) {
diff --git a/system/include/emscripten/emscripten.h b/system/include/emscripten/emscripten.h
index ac880981..ddcbc43a 100644
--- a/system/include/emscripten/emscripten.h
+++ b/system/include/emscripten/emscripten.h
@@ -24,17 +24,38 @@ extern "C" {
  *    EM_ASM(window.alert('hai'));
  *
  * This also works with asm.js, as it outlines the code (it
- * does a function call to reach it).
+ * does a function call to reach it). It supports newlines,
  *
- * Notes: double-quotes (") are not supported, but you can use
+ *    EM_ASM(
+ *      window.alert('hai'));
+ *      window.alert('bai'));
+ *    )
+ *
+ * Notes: Double-quotes (") are not supported, but you can use
  *        single-quotes (') in js anyhow.
  *
- *        you can't access C variables with EM_ASM, use gcc
- *        inline asm for that, asm("code" : .. etc.)
+ *        You can't access C variables with EM_ASM, nor receive
+ *        a value back. use EM_ASM_INT or EM_ASM_DOUBLE for that
  */
 #define EM_ASM(...) emscripten_asm_const(#__VA_ARGS__)
 
 /*
+ * Input-output versions of EM_ASM. EM_ASM_INT receives arguments of
+ * either int or double type and returns an int; EM_ASM_DOUBLE
+ * receives similar arguments (int or double) but returns a double.
+ * Arguments arrive as $0, $1 etc; output value should be returned:
+ *
+ *    int x = EM_ASM_INT({
+ *      console.log('I received: ' + [$0, $1]);
+ *      return $0 + $1;
+ *    }, calc(), otherCalc());
+ *
+ * Note the {,}
+ */
+#define EM_ASM_INT(code, ...) emscripten_asm_const_int(#code, __VA_ARGS__)
+#define EM_ASM_DOUBLE(code, ...) emscripten_asm_const_double(#code, __VA_ARGS__)
+
+/*
  * Forces LLVM to not dead-code-eliminate a function. Note that
  * you still need to use EXPORTED_FUNCTIONS so it stays alive
  * in JS, e.g.
@@ -423,6 +444,8 @@ void emscripten_jcache_printf_(...); /* internal use */
 
 /* Helper API for EM_ASM - do not call this yourself */
 void emscripten_asm_const(const char *code);
+int emscripten_asm_const_int(const char *code, ...);
+double emscripten_asm_const_double(const char *code, ...);
 
 #ifdef __cplusplus
 }
diff --git a/tests/test_core.py b/tests/test_core.py
index d7b6cf53..67e316e4 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -3970,7 +3970,7 @@ def process(filename):
       #include <stdio.h>
       #include <emscripten.h>
 
-      int main() {
+      int main(int argc, char **argv) {
         EM_ASM(Module.print('hello dere1'));
         EM_ASM(
           Module.print('hello dere2');
@@ -3981,11 +3981,19 @@ def process(filename):
             Module.print('hello dere' + 4);
           );
         }
+        int sum = 0;
+        for (int i = 0; i < argc*3; i++) {
+          sum += EM_ASM_INT({
+            Module.print('i: ' + [$0, ($1).toFixed(2)]);
+            return $0*2;
+          }, i, double(i)/12);
+        }
+        printf("sum: %d\n", sum);
         return 0;
       }
       '''
 
-    self.do_run(src, 'hello dere1\nhello dere2\nhello dere3\nhello dere4\nhello dere3\nhello dere4\nhello dere3\nhello dere4\n')
+    self.do_run(src, 'hello dere1\nhello dere2\nhello dere3\nhello dere4\nhello dere3\nhello dere4\nhello dere3\nhello dere4\ni: 0,0.00\ni: 1,0.08\ni: 2,0.17\nsum: 6\n')
 
   def test_memorygrowth(self):
     if Settings.USE_TYPED_ARRAYS == 0: return self.skip('memory growth is only supported with typed arrays')