optimize Pointer_make (both input size and processing time)

1 files changed, 26 insertions, 2 deletions

diff --git a/src/parseTools.js b/src/parseTools.js
index 4db740db..6ae0e5d3 100644
--- a/src/parseTools.js
+++ b/src/parseTools.js
@@ -585,7 +585,7 @@ function generateStructTypes(type) {
       ret = ret.concat(zeros(typeData.flatIndexes[i+1] - ret.length));
     }
   }
-  return ret;
+  return ret.concat(zeros(typeData.flatSize - ret.length));
 }
 
 // Flow blocks
@@ -819,7 +819,31 @@ function makePointer(slab, pos, allocator, type) {
   assert(type, 'makePointer requires type info');
   if (slab.substr(0, 4) === 'HEAP' || (USE_TYPED_ARRAYS == 1 && slab in set('IHEAP', 'FHEAP'))) return pos;
   var types = generateStructTypes(type);
-  if (dedup(types).length === 1) types = types[0];
+
+  // compress type info and data if possible
+  var de;
+  try {
+    // compress all-zeros into a number (which will become zeros(..)).
+    // note that we cannot always eval the slab, e.g., if it contains ident,0,0 etc. In that case, no compression TODO: ensure we get arrays here, not str
+    var evaled = typeof slab === 'string' ? eval(slab) : slab;
+    de = dedup(evaled);
+    if (de.length === 1 && de[0] === 0) {
+      slab = evaled.length;
+    }
+    // TODO: if not all zeros, at least filter out items with type === 0. requires cleverness to know how to skip at runtime though. also
+    //       be careful of structure padding
+  } catch(e){}
+  de = dedup(types);
+  if (de.length === 1) {
+    types = de[0];
+  } else if (de.length === 2 && typeof slab === 'number') {
+    // If slab is all zeros, we can compress types even if we have i32,0,0,0,i32,0,0,0 etc. - we do not need the zeros
+    de = de.filter(function(x) { return x !== 0 });
+    if (de.length === 1) {
+      types = de[0];
+    }
+  }
+
   return 'Pointer_make(' + slab + ', ' + (pos ? pos : 0) + (allocator ? ', ' + allocator : '') + ', ' +
          JSON.stringify(types) +
          ')';