1.0.4.66: Undo D-X changes in 1.0.4.63

[sbcl.git] / OPTIMIZATIONS

diff --git a/OPTIMIZATIONS b/OPTIMIZATIONS
index cb963ea..631501c 100644 (file)
--- a/OPTIMIZATIONS
+++ b/OPTIMIZATIONS
@@ -224,6 +224,12 @@ Initialization of stack-allocated arrays is inefficient: we always
 fill the vector with zeroes, even when it is not needed (as for
 platforms with conservative GC or for arrays of unboxed objectes) and
 is performed later explicitely.
+
+(This is harder than it might look at first glance, as MAKE-ARRAY is smart
+enough to eliminate something like ':initial-element 0'.  Such an optimization
+is valid if the vector is being allocated in the heap, but not if it is being
+allocated on the stack.  You could remove this optimization, but that makes
+the heap-allocated case somewhat slower...)
 --------------------------------------------------------------------------------
 #28
 a. Accessing raw slots in structure instances is more inefficient than
@@ -403,3 +409,10 @@ comparison VOP receives an TN of the appropriate storage class.
 Obviously, it would be better if a) we only performed one MOV prior to
 all three comparisons or b) eliminated the necessity of the MOV(s)
 altogether.  The former option is probably easier than the latter.
+
+--------------------------------------------------------------------------------
+#37
+
+Dynamic extent allocation doesn't currently work for one-element lists,
+since there's a source transform from (LIST X) to (CONS X NIL).
+