X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=OPTIMIZATIONS;h=51fcb32f0e2a426469ae07f97796e3b2d1685a19;hb=51c5280a4b41f8c51d434643cde3e18af4113473;hp=bb50f42b7e30d6568afc9104dd128c7ecd4806f1;hpb=caf8bb05a82659e688c125b418783bc8a3bd2be8;p=sbcl.git

diff --git a/OPTIMIZATIONS b/OPTIMIZATIONS
index bb50f42..51fcb32 100644
--- a/OPTIMIZATIONS
+++ b/OPTIMIZATIONS
@@ -1,3 +1,4 @@
+#1
 (defun mysl (s)
     (declare (simple-string s))
     (declare (optimize (speed 3) (safety 0) (debug 0)))
@@ -10,14 +11,12 @@
 
 * On X86 I is represented as a tagged integer.
 
-* EQL uses "CMP reg,reg" instead of "CMP reg,im". This causes
-  allocation of extra register and extra move.
-
 * Unnecessary move:
   3: SLOT S!11[EDX] {SB-C::VECTOR-LENGTH 1 7} => t23[EAX]
   4: MOVE t23[EAX] => t24[EBX]
 
 --------------------------------------------------------------------------------
+#2
 (defun quux (v)
   (declare (optimize (speed 3) (safety 0) (space 2) (debug 0)))
   (declare (type (simple-array double-float 1) v))
@@ -34,6 +33,7 @@
   and emits costy MOVE ... => FR1.
 
 --------------------------------------------------------------------------------
+#3
 (defun bar (n)
   (declare (optimize (speed 3) (safety 0) (space 2))
            (type fixnum n))
@@ -42,10 +42,8 @@
     (length v)))
 
 * IR1 does not optimize away (MAKE-LIST N).
-
-* IR1 thinks that the type of V in (LENGTH V) is (OR LIST SIMPLE-VECTOR), not
-  SIMPLE-VECTOR.
 --------------------------------------------------------------------------------
+#4
 (defun bar (v1 v2)
   (declare (optimize (speed 3) (safety 0) (space 2))
            (type (simple-array base-char 1) v1 v2))
@@ -63,3 +61,98 @@ VOP DATA-VECTOR-SET/SIMPLE-STRING V2!14[EDI] t32[EAX] t30[S2]>t33[CL]
   last two moves.
 
 * And why two moves?
+--------------------------------------------------------------------------------
+#6
+09:49:05 <jtra> I have found a case in those where suboptimal code is
+  generate with nested loops, it might be moderately easy to fix that
+09:49:28 <jtra> see
+  http://www.bagley.org/~doug/shootout/bench/nestedloop/nestedloop.cmucl
+09:50:30 <jtra> if you add declarations to dotimes, generated code is
+  almost optimal, but most inner loops run out of registers and use
+  memory location for iteration variable
+
+;;; -*- mode: lisp -*-
+;;; http://www.bagley.org/~doug/shootout/
+;;; from Friedrich Dominicus
+
+(defun main ()
+  (let ((n (parse-integer (or (car (last extensions:*command-line-strings*)) "1")))
+        (x 0))
+    (declare (fixnum n)
+             (fixnum x)
+             (optimize (speed 3) (debug 0) (safety 0)))
+    (dotimes (a n)
+      (dotimes (b n)
+        (dotimes (c n)
+          (dotimes (d n)
+            (dotimes (e n)
+              (dotimes (f n)
+                (incf x)))))))
+   (format t "~A~%" x)))
+--------------------------------------------------------------------------------
+#8
+(defun foo (d)
+  (declare (optimize (speed 3) (safety 0) (debug 0)))
+  (declare (type (double-float 0d0 1d0) d))
+  (loop for i fixnum from 1 to 5
+        for x1 double-float = (sin d) ;;; !!!
+        do (loop for j fixnum from 1 to 4
+                 sum x1 double-float)))
+
+Without the marked declaration Python will use boxed representation for X1.
+
+This is equivalent to
+
+(let ((x nil))
+  (setq x 0d0)
+  ;; use of X as DOUBLE-FLOAT
+)
+
+The initial binding is effectless, and without it X is of type
+DOUBLE-FLOAT. Unhopefully, IR1 does not optimize away effectless
+SETs/bindings, and IR2 does not perform type inference.
+--------------------------------------------------------------------------------
+#9 "Multi-path constant folding"
+(defun foo (x)
+  (if (= (cond ((irgh x) 0)
+               ((buh x) 1)
+               (t 2))
+         0)
+      :yes
+      :no))
+
+This code could be optimized to
+
+(defun foo (x)
+  (cond ((irgh x) :yes)
+        ((buh x) :no)
+        (t :no)))
+--------------------------------------------------------------------------------
+#11
+(inverted variant of #9)
+
+(lambda (x)
+  (let ((y (sap-alien x c-string)))
+    (list (alien-sap y)
+          (alien-sap y))))
+
+It could be optimized to
+
+(lambda (x) (list x x))
+
+(if Y were used only once, the current compiler would optimize it)
+--------------------------------------------------------------------------------
+#12
+(typep (truly-the (simple-array * (*)) x) 'simple-vector)
+
+tests lowtag.
+--------------------------------------------------------------------------------
+#13
+FAST-+/FIXNUM and similar should accept unboxed arguments in interests
+of representation selection. Problem: inter-TN dependencies.
+--------------------------------------------------------------------------------
+#14
+The derived type of (/ (THE (DOUBLE-FLOAT (0D0)) X) (THE (DOUBLE-FLOAT
+1D0) Y)) is (DOUBLE-FLOAT 0.0d0). While it might be reasonable, it is
+better to derive (DOUBLE-FLOAT (-0.0d0)).
+--------------------------------------------------------------------------------