[Sbcl-commits] CVS: sbcl/doc/internals calling-convention.texinfo, 1.3, 1.4

[Gabor M. <me...@us...>]

Update of /cvsroot/sbcl/sbcl/doc/internals
In directory fdv4jf1.ch3.sourceforge.com:/tmp/cvs-serv27588/doc/internals

Modified Files:
	calling-convention.texinfo 
Log Message:
1.0.27.17: faster local calls on x86/x86-64

Instead of JMPing to TARGET, CALL a trampoline that saves the return
pc and jumps. Although this is an incredibly stupid trick, the paired
CALL/RET instructions are a big win.


Index: calling-convention.texinfo
===================================================================
RCS file: /cvsroot/sbcl/sbcl/doc/internals/calling-convention.texinfo,v
retrieving revision 1.3
retrieving revision 1.4
diff -u -d -r1.3 -r1.4
--- calling-convention.texinfo	21 Apr 2009 11:25:52 -0000	1.3
+++ calling-convention.texinfo	21 Apr 2009 11:33:38 -0000	1.4
@@ -212,9 +212,11 @@
 @comment  node-name,  next,  previous,  up
 @section Additional Notes
 
-The low-hanging fruit here is going to be changing every call and
-return to use @code{CALL} and @code{RETURN} instructions instead of
-@code{JMP} instructions.
+The low-hanging fruit is going to be changing every call and return to
+use @code{CALL} and @code{RETURN} instructions instead of @code{JMP}
+instructions which is partly done on x86oids: a trampoline is
+@code{CALL}ed and that @code{JMP}s to the target which is sufficient
+to negate (most of?) the penalty.
 
 A more involved change would be to reduce the number of argument
 passing registers from three to two, which may be beneficial in terms