only include i64 precise code if it will actually be used

3 files changed, 11 insertions, 3 deletions

diff --git a/src/jsifier.js b/src/jsifier.js
index dcc853f2..8caab6e2 100644
--- a/src/jsifier.js
+++ b/src/jsifier.js
@@ -38,7 +38,6 @@ function JSify(data, functionsOnly, givenFunctions) {
     var preFile = BUILD_AS_SHARED_LIB ? 'preamble_sharedlib.js' : 'preamble.js';
     var pre = processMacros(preprocess(read(preFile).replace('{{RUNTIME}}', getRuntime())));
     print(pre);
-    if (PRECISE_I64_MATH) print(read('long.js'));
 
     Functions.implementedFunctions = set(data.unparsedFunctions.map(function(func) { return func.ident }));
   }
@@ -1200,6 +1199,12 @@ function JSify(data, functionsOnly, givenFunctions) {
     // This is the main pass. Print out the generated code that we have here, together with the
     // rest of the output that we started to print out earlier (see comment on the
     // "Final shape that will be created").
+    if (PRECISE_I64_MATH && preciseI64MathUsed) {
+      print(read('long.js'));
+    } else {
+      print('// Warning: printing of i64 values may be slightly rounded! No deep i64 math used, so precise i64 code not included');
+      print('var i64Math = null;');
+    }
     var generated = itemsDict.functionStub.concat(itemsDict.GlobalVariablePostSet);
     generated.forEach(function(item) { print(indentify(item.JS || '', 2)); });
     if (RUNTIME_TYPE_INFO) {
diff --git a/src/library.js b/src/library.js
index f49a8a58..be5e48d7 100644
--- a/src/library.js
+++ b/src/library.js
@@ -2507,12 +2507,12 @@ LibraryManager.library = {
           var prefix = '';
           if (next == 'd'.charCodeAt(0) || next == 'i'.charCodeAt(0)) {
 #if PRECISE_I64_MATH == 1
-            if (argSize == 8) argText = i64Math.stringify(origArg[0], origArg[1]); else
+            if (argSize == 8 && i64Math) argText = i64Math.stringify(origArg[0], origArg[1]); else
 #endif
             argText = reSign(currArg, 8 * argSize, 1).toString(10);
           } else if (next == 'u'.charCodeAt(0)) {
 #if PRECISE_I64_MATH == 1
-            if (argSize == 8) argText = i64Math.stringify(origArg[0], origArg[1], true); else
+            if (argSize == 8 && i64Math) argText = i64Math.stringify(origArg[0], origArg[1], true); else
 #endif
             argText = unSign(currArg, 8 * argSize, 1).toString(10);
             currArg = Math.abs(currArg);
diff --git a/src/parseTools.js b/src/parseTools.js
index 5ec3b4ed..22f38207 100644
--- a/src/parseTools.js
+++ b/src/parseTools.js
@@ -1560,6 +1560,8 @@ function isSignedOp(op, variant) {
 }
 
 var legalizedI64s = USE_TYPED_ARRAYS == 2; // We do not legalize globals, but do legalize function lines. This will be true in the latter case
+var preciseI64MathUsed = false; // Set to true if we actually use precise i64 math: If PRECISE_I64_MATH is set, and also such math is actually
+                                // needed (+,-,*,/,% - we do not need it for bitops)
 
 function processMathop(item) {
   var op = item.op;
@@ -1617,6 +1619,7 @@ function processMathop(item) {
       }
     }
     function i64PreciseOp(type, lastArg) {
+      preciseI64MathUsed = true;
       return finish(['(i64Math.' + type + '(' + low1 + ',' + high1 + ',' + low2 + ',' + high2 +
                      (lastArg ? ',' + lastArg : '') + '),i64Math.result[0])', 'i64Math.result[1]']);
     }