0.6.12.13:

[sbcl.git] / src / compiler / x86 / sap.lisp

diff --git a/src/compiler/x86/sap.lisp b/src/compiler/x86/sap.lisp
index daf9be8..b9e6bcd 100644 (file)
--- a/src/compiler/x86/sap.lisp
+++ b/src/compiler/x86/sap.lisp
@@ -10,9 +10,6 @@
 ;;;; files for more information.
 
 (in-package "SB!VM")
-
-(file-comment
- "$Header$")
 \f
 ;;;; moves and coercions
 
@@ -79,6 +76,12 @@
 \f
 ;;;; SAP-INT and INT-SAP
 
+;;; The function SAP-INT is used to generate an integer corresponding
+;;; to the system area pointer, suitable for passing to the kernel
+;;; interfaces (which want all addresses specified as integers). The
+;;; function INT-SAP is used to do the opposite conversion. The
+;;; integer representation of a SAP is the byte offset of the SAP from
+;;; the start of the address space.
 (define-vop (sap-int)
   (:args (sap :scs (sap-reg) :target int))
   (:arg-types system-area-pointer)
@@ -88,7 +91,6 @@
   (:policy :fast-safe)
   (:generator 1
     (move int sap)))
-
 (define-vop (int-sap)
   (:args (int :scs (unsigned-reg) :target sap))
   (:arg-types unsigned-num)