[Sbcl-commits] CVS: sbcl/src/compiler/generic early-objdef.lisp,1.17,1.18

[Christophe R. <cr...@us...>]

Update of /cvsroot/sbcl/sbcl/src/compiler/generic
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv5388/src/compiler/generic

Modified Files:
	early-objdef.lisp 
Log Message:
0.8.8.10:
	MORE MICRO-OPTIMIZATION
	... renumber all widetags.  (LESS BINARY-COMPATIBILITY)
	... implement some smarter type tag checking on the x86.

	The smarter type checking comes in several flavours.

	* If we have two adjacent lowtags, in three cases out of four
	  we can do "and, cmp, branch", rather than 
	  "cmp, branch, cmp, branch";
	* If we have two lowtags that are unadjacent but differ by
	  just one bit, we can likewise do "and, cmp, branch" rather 
	  than "cmp, branch, cmp, branch";
	* If we have a contiguous range of lowtags that includes the
	  most positive lowtag, we do not need to test the upper bound;
	* If we have four lowtags with only two bits different, we can
	  do "and, cmp, branch" rather than *four* "cmp, branch" pairs.

	This change will conflict with ongoing 64-bit ports.  The 
	conflict is resolvable (there are enough widetags in the "array"
	range (which in practice is 130 - 254; currently there are five
	in this range unused (or three with long-float arrays)


Index: early-objdef.lisp
===================================================================
RCS file: /cvsroot/sbcl/sbcl/src/compiler/generic/early-objdef.lisp,v
retrieving revision 1.17
retrieving revision 1.18
diff -u -d -r1.17 -r1.18
--- early-objdef.lisp	10 Oct 2003 07:33:33 -0000	1.17
+++ early-objdef.lisp	1 Mar 2004 23:22:25 -0000	1.18
@@ -58,6 +58,41 @@
 ;;; the heap types, stored in 8 bits of the header of an object on the
 ;;; heap, to identify the type of the heap object (which'll be at
 ;;; least two machine words, often more)
+;;;
+;;; Note: the order specified here is not critical for correctness,
+;;; but (FIXME) with %TEST-HEADERS as currently defined, BIGNUM must
+;;; be first, and COMPLEX-ARRAY must be last.
+;;;
+;;; However, for efficiency, we prefer contiguous sets of widetags for
+;;; "similar" objects, so that type checking can be done with a range
+;;; check, rather than several individual checks.
+;;;
+;;; * BIGNUM + RATIO (+ FIXNUM) = RATIONAL
+;;;
+;;; * SINGLE-FLOAT + DOUBLE-FLOAT + LONG-FLOAT = FLOAT
+;;;
+;;; * RATIONAL + FLOAT = REAL
+;;;
+;;; * (FIXME: COMPLEX example, which needs fixing anyway -- see
+;;;   UPGRADED-COMPLEX-PART-TYPE)
+;;;
+;;; * SIMPLE-ARRAY-* = (SIMPLE-ARRAY * (*))
+;;;
+;;; * SIMPLE-ARRAY-NIL + SIMPLE-BASE-STRING = SIMPLE-STRING
+;;;
+;;; * SIMPLE-ARRAY + COMPLEX-ARRAYOID = (SATISFIES ARRAY-HEADER-P)
+;;;
+;;; In addition, with
+;;; sufficient care we can cause extra combinations to appear with
+;;; differences in only one bit, permitting a more efficient type
+;;; test.  As an example, if SIMPLE-BASE-STRING = 0xA6 and
+;;; COMPLEX-BASE-STRING = 0xE6, then the type test for BASE-STRING is
+;;;
+;;;   AND   tag, ~0x40, tag
+;;;   ANDcc tag,  0xA6, tag
+;;;   JNE   tag, label
+;;;
+;;; rather than two separate tests and jumps 
 (defenum (:suffix -widetag
 	  :start (+ (ash 1 n-lowtag-bits) other-immediate-0-lowtag)
 	  :step (ash 1 (1- n-lowtag-bits)))
@@ -71,17 +106,47 @@
   complex-double-float
   #!+long-float complex-long-float
 
-  simple-array
-  simple-array-nil
-  simple-base-string
-  simple-bit-vector
-  simple-vector
+  code-header
+  simple-fun-header
+  closure-header
+  funcallable-instance-header
+
+  return-pc-header
+  value-cell-header
+  symbol-header
+  base-char
+  sap
+  unbound-marker
+  weak-pointer
+  instance-header
+  fdefn
+
+  unused00
+  unused01
+  unused02
+  unused03
+  unused04
+  unused05
+  unused06
+  unused07
+  #!-long-float unused08
+  #!-long-float unused09
+  
+  #!+long-float simple-array-long-float
+  #!+long-float simple-array-complex-long-float
+  #!-long-float unused10
+  #!-long-float unused11
+
   simple-array-unsigned-byte-2
   simple-array-unsigned-byte-4
   simple-array-unsigned-byte-7
   simple-array-unsigned-byte-8
   simple-array-unsigned-byte-15
   simple-array-unsigned-byte-16
+  simple-array-nil
+  simple-base-string
+  simple-bit-vector
+  simple-vector
   simple-array-unsigned-byte-29
   simple-array-unsigned-byte-31
   simple-array-unsigned-byte-32
@@ -91,31 +156,15 @@
   simple-array-signed-byte-32
   simple-array-single-float
   simple-array-double-float
-  #!+long-float simple-array-long-float
   simple-array-complex-single-float
   simple-array-complex-double-float
-  #!+long-float simple-array-complex-long-float
-  complex-base-string
+  simple-array
   complex-vector-nil
+  complex-base-string
   complex-bit-vector
   complex-vector
   complex-array
-
-  code-header
-  simple-fun-header
-  closure-header
-  funcallable-instance-header
-  nil ; this was closure-fun-header; remove when +FASL-FILE-VERSION+ will increase
-
-  return-pc-header
-  value-cell-header
-  symbol-header
-  base-char
-  sap
-  unbound-marker
-  weak-pointer
-  instance-header
-  fdefn)
+)
 
 ;;; the different vector subtypes
 (defenum (:prefix vector- :suffix -subtype)