make FAST_MEMORY and TOTAL_MEMORY easier to use; fix slowdown in dlmalloc benchmark

2 files changed, 10 insertions, 4 deletions

diff --git a/src/preamble.js b/src/preamble.js
index 59389e58..54011558 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -428,7 +428,8 @@ var STACK_ROOT, STACKTOP, STACK_MAX;
 var STATICTOP;
 
 var HAS_TYPED_ARRAYS = false;
-var TOTAL_MEMORY = 50*1024*1024;
+var TOTAL_MEMORY = Module['TOTAL_MEMORY'] || {{{ TOTAL_MEMORY }}};
+var FAST_MEMORY = Module['FAST_MEMORY'] || {{{ FAST_MEMORY }}};
 
 // Initialize the runtime's memory
 #if USE_TYPED_ARRAYS
@@ -459,9 +460,8 @@ if (HAS_TYPED_ARRAYS) {
 } else
 #endif
 {
-  // Without this optimization, Chrome is slow. Sadly, the constant here needs to be tweaked depending on the code being run...
-  var FAST_MEMORY = TOTAL_MEMORY/32;
-  HEAP = new Array(FAST_MEMORY);
+  // Make sure that our HEAP is implemented as a flat array.
+  HEAP = new Array(TOTAL_MEMORY);
   for (var i = 0; i < FAST_MEMORY; i++) {
     HEAP[i] = 0; // XXX We do *not* use {{| makeSetValue(0, 'i', 0, 'null') |}} here, since this is done just to optimize runtime speed
   }
diff --git a/src/settings.js b/src/settings.js
index 1b1665bc..ab532e67 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -34,6 +34,12 @@ INVOKE_RUN = 1; // Whether we will call run(). Disable if you embed the generate
                 // code in your own, and will call run() yourself at the right time
 INIT_STACK = 1; // Whether to initialize memory on the stack to 0.
 INIT_HEAP = 0; // Whether to initialize memory anywhere other than the stack to 0.
+FAST_MEMORY = 2*1024*1024; // The amount of memory to initialize to 0. This ensures it will be
+                           // in a flat array. This only matters in non-typed array builds.
+TOTAL_MEMORY = 50*1024*1024; // The total amount of memory to use. This mainly matters in
+                             // typed array builds - accessing memory about this value will
+                             // return undefined values and lead to serious problems, and there
+                             // is currently no warning about that!
 
 // Code embetterments
 OPTIMIZE = 0; // Optimize llvm operations into js commands