Changeset 21096 in webkit for trunk/JavaScriptCore/wtf/FastMalloc.cpp

Timestamp:

Apr 25, 2007, 1:25:06 PM (18 years ago)

Author:

darin

Message:

Reviewed by Geoff.

• tweak the allocator for a small speedup -- Shark showed this was a win, but I can't measure an improvement right now, but it's also clear these changes do no harm

• wtf/FastMalloc.cpp: (WTF::LgFloor): Use ALWAYS_INLINE here; in testing I did a while back this was necessary to get this single-instruction function to be inlined. (WTF::SizeClass): Use ALWAYS_INLINE here too for the same reason. Also change the special case for a size of 0 to work without a branch for a bit of extra speed. (WTF::ByteSizeForClass): Use ALWAYS_INLINE here too for the same reason.

File:

• trunk/JavaScriptCore/wtf/FastMalloc.cpp (modified) (4 diffs)

trunk/JavaScriptCore/wtf/FastMalloc.cpp

@@ -286 +286 @@
 // Return floor(log2(n)) for n > 0.
 #if PLATFORM(X86) && COMPILER(GCC)
-static inline int LgFloor(size_t n) {
+static ALWAYS_INLINE int LgFloor(size_t n) {
   // "ro" for the input spec means the input can come from either a
   // register ("r") or offsetable memory ("o").
@@ -299 +299 @@
 
 #elif PLATFORM(PPC) && COMPILER(GCC)
-static inline int LgFloor(size_t n) {
+static ALWAYS_INLINE int LgFloor(size_t n) {
   // "r" for the input spec means the input must come from a
   // register ("r")
@@ -329 +329 @@
 #endif
 
-static inline size_t SizeClass(size_t size) {
-  if (size == 0) size = 1;
+static ALWAYS_INLINE size_t SizeClass(size_t size) {
+  size += !size; // change 0 to 1 (with no branches)
   const int lg = LgFloor(size);
   const int align = size_shift[lg];
@@ -337 +337 @@
 
 // Get the byte-size for a specified class
-static inline size_t ByteSizeForClass(size_t cl) {
+static ALWAYS_INLINE size_t ByteSizeForClass(size_t cl) {
   return class_to_size[cl];
 }