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| author | Paul Eggert <eggert@cs.ucla.edu> | 2015-01-05 09:07:45 -0800 |
|---|---|---|
| committer | Paul Eggert <eggert@cs.ucla.edu> | 2015-01-05 10:15:04 -0800 |
| commit | bc78ff2603b8c062dbd8f93f421c3412e36e343f (patch) | |
| tree | 52f5ad17e9a61db8287ed4a026abfb4dc64ccd16 /src/ChangeLog | |
| parent | 58f2d6ef32b28a787fcc4e0d98b3f331ceb2a68c (diff) | |
| download | emacs-bc78ff2603b8c062dbd8f93f421c3412e36e343f.tar.gz | |
Use 0 for Qnil
Fixes Bug#15880.
If USE_LSB_TAG, arrange for the representation of Qnil to be zero so
that NILP (x) is equivalent to testing whether x is 0 at the
machine level. The overall effects of this and the previous patch
shrink the size of the text segment by 2.3% and speeds up
compilation of all the .elc files by about 0.5% on my platform,
which is Fedora 20 x86-64.
* lib-src/make-docfile.c (compare_globals):
* src/lisp.h (lisp_h_XPNTR, lisp_h_XSYMBOL, lisp_h_XUNTAG)
(make_lisp_symbol) [USE_LSB_TAG]:
Symbols now tag the difference from lispsym, not the pointer.
(lisp_h_XUNTAGBASE, TAG_SYMPTR): New macros.
(Lisp_Int0, Lisp_Int1, Lisp_Symbol, Lisp_Misc, Lisp_String, Lisp_Cons):
Renumber so that Lisp_Symbol is 0, so that Qnil is zero.
(XSYMBOL): New forward decl.
(XUNTAGBASE): New function.
(XUNTAG): Use it.
Diffstat (limited to 'src/ChangeLog')
| -rw-r--r-- | src/ChangeLog | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/src/ChangeLog b/src/ChangeLog index 62737994747..b068056667b 100644 --- a/src/ChangeLog +++ b/src/ChangeLog @@ -1,5 +1,23 @@ 2015-01-05 Paul Eggert <eggert@cs.ucla.edu> + Use 0 for Qnil + Fixes Bug#15880. + If USE_LSB_TAG, arrange for the representation of Qnil to be zero so + that NILP (x) is equivalent to testing whether x is 0 at the + machine level. The overall effects of this and the previous patch + shrink the size of the text segment by 2.3% and speeds up + compilation of all the .elc files by about 0.5% on my platform, + which is Fedora 20 x86-64. + * lisp.h (lisp_h_XPNTR, lisp_h_XSYMBOL, lisp_h_XUNTAG) + (make_lisp_symbol) [USE_LSB_TAG]: + Symbols now tag the difference from lispsym, not the pointer. + (lisp_h_XUNTAGBASE, TAG_SYMPTR): New macros. + (Lisp_Int0, Lisp_Int1, Lisp_Symbol, Lisp_Misc, Lisp_String, Lisp_Cons): + Renumber so that Lisp_Symbol is 0, so that Qnil is zero. + (XSYMBOL): New forward decl. + (XUNTAGBASE): New function. + (XUNTAG): Use it. + Compute C decls for DEFSYMs automatically Fixes Bug#15880. This patch also makes Q constants (e.g., Qnil) constant addresses |