1.0.46.43: fix sb-introspect on non-threaded builds

[sbcl.git] / OPTIMIZATIONS

diff --git a/OPTIMIZATIONS b/OPTIMIZATIONS
index 55f86c4..81ab61d 100644 (file)
--- a/OPTIMIZATIONS
+++ b/OPTIMIZATIONS
@@ -209,6 +209,10 @@ 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...)
+
+To do this, extend ALLOCATE-VECTOR with ALLOW-JUNK argument, and when
+stack allocating don't zero if it is true -- and probably ALLOW-JUNK iff
+the vector is a specialized one (cannot have pointers.)
 --------------------------------------------------------------------------------
 #28
 a. Accessing raw slots in structure instances is more inefficient than
@@ -401,3 +405,23 @@ can be transformed into
 which allows compiler-macro-expansion for FOO. (Only constant
 arguments can be moved inside the new lambda -- otherwise evaluation
 order is altered.)
+
+--------------------------------------------------------------------------------
+#41
+
+The unibyte external formats are written in a very generic way.  Three
+optimizations immediately applicable that could be automatically
+generated:
+
+(a) if the external format merely permutes the first 256 characters, a
+    constant-time lookup (rather than a binary search) could be
+    performed on output.  This applies at least to EBCDIC, which
+    currently has a hand-rolled mapper instead.
+
+(b) if there are no undefined characters corresponding to the 256
+    codes, then no error checking need be done on input.
+
+(c) if there is a way to use particular bits of the exceptional
+    characters, constant-time output (rather than binary search) can
+    still be achieved as used to be done by the latin-9 external
+    format before 1.0.31.