do not wind/unwind stacks if initial stack size is 0; 20% speedup

3 files changed, 12 insertions, 5 deletions

diff --git a/src/analyzer.js b/src/analyzer.js
index 2a0ee701..8d77b13d 100644
--- a/src/analyzer.js
+++ b/src/analyzer.js
@@ -313,10 +313,11 @@ function analyzer(data) {
         var total = 0;
         var lines = func.labels[0].lines;
         for (var i = 0; i < lines.length; i++) {
-          var item = lines[i].value;
+          var line = lines[i];
+          var item = line.value;
           if (!item || item.intertype != 'alloca') break;
-          // FIXME: This ignores nativized variables, but probably negligible
-          item.allocatedSize = calcAllocatedSize(item.allocatedType, data.types);
+          item.allocatedSize = func.variables[line.ident].impl === VAR_EMULATED ?
+            calcAllocatedSize(item.allocatedType, data.types) : 0;
           total += item.allocatedSize;
         }
         func.initialStack = total;
diff --git a/src/jsifier.js b/src/jsifier.js
index 597b0c31..32b284ad 100644
--- a/src/jsifier.js
+++ b/src/jsifier.js
@@ -546,7 +546,7 @@ function JSify(data) {
     return ret;
   });
   makeFuncLineZyme('return', function(item) {
-    var ret = RuntimeGenerator.stackExit() + '\n';
+    var ret = RuntimeGenerator.stackExit(item.funcData.initialStack) + ';\n';
     if (LABEL_DEBUG) ret += "INDENT = INDENT.substr(0, INDENT.length-2);\n";
     ret += 'return';
     if (item.value) {
@@ -583,6 +583,7 @@ function JSify(data) {
   });
   makeFuncLineZyme('alloca', function(item) {
     assert(typeof item.allocatedIndex === 'number'); // or, return RuntimeGenerator.stackAlloc(calcAllocatedSize(item.allocatedType, TYPES));
+    if (item.allocatedSize === 0) return ''; // This will not actually be shown - it's nativized
     return getFastValue('STACKTOP', '-', item.allocatedIndex.toString());
   });
   makeFuncLineZyme('phi', function(item) {
diff --git a/src/runtime.js b/src/runtime.js
index 0ae70fa3..d6a545c2 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -26,6 +26,10 @@ RuntimeGenerator = {
   },
 
   stackEnter: function(initial) {
+    if (initial === 0) return ''; // XXX Note that we don't even push the stack! This is faster, but
+                                  // means that we don't clear stack allocations done in this function
+                                  // until the parent unwinds its stack. So potentially if we are in
+                                  // a loop, we can use a lot of memory.
     var ret = 'STACK_STACK.push(STACKTOP); STACKTOP += ' + initial;
     if (GUARD_MEMORY) {
       ret += '; assert(STACKTOP < STACK_MAX)';
@@ -33,7 +37,8 @@ RuntimeGenerator = {
     return ret;
   },
 
-  stackExit: function() {
+  stackExit: function(initial) {
+    if (initial === 0) return ''; // XXX See comment in stackEnter
     return 'STACKTOP = STACK_STACK.pop();';
   },