Some generated files have a lot of dependencies and a lot of
dependents. For this case it is worth doing a micro optimization to
detect if the generated contents have changed since the last time.
The obvious example is asm-offsets.h. Most asm-offsets.h have large
dependency trees, arch/i386/asm-offsets.s depends on 160 .h files plus
their config options (our include tree is spaghetti), yet a change to
most of those files has no effect on the generated asm-offsets.h. IA64
is even worse, with a larger dependency list for asm-offsets.s and more
files affected by a change to asm-offsets.h.
This patch against kbuild 2.5-2.4.13-1 adds update_if_changed(). Take
a look at it before I release it to the world.
Index: 13.11/Documentation/kbuild/kbuild-2.5.txt
--- 13.11/Documentation/kbuild/kbuild-2.5.txt Sun, 28 Oct 2001 21:02:09 +1100 kaos
(linux-2.4/G/e/50_kbuild-2.5 1.32 644)
+++ 13.12(w)/Documentation/kbuild/kbuild-2.5.txt Mon, 29 Oct 2001 01:47:41 +1100 kaos
+(linux-2.4/G/e/50_kbuild-2.5 1.33 644)
@@ -564,6 +564,25 @@ MAKEFILE.IN SYNTAX
base_target(vmlinux) is semi-reserved, it can be specified in a
makefile but it always refers to the top level vmlinux.
+ update_if_changed(target new_target)
+ If the new_target is newer than target and they are not identical
+ then replace the contents of target with the contents of new_target.
+ This command is normally used for text files generated by
+ user_command(), the new_target is generated but only replaces target
+ if anything has changed. The new_target parameter can be omitted, it
+ defaults to the target name prefixed with 'tmp_' (not '.tmp_').
+
+ Obviously there must be another command that generates new_target.
+ Do not use a new_target name that starts with '.', dot files are
+ special cases in kbuild and will not do what you expect. The target
+ is automatically marked as nodepend(), the only thing it depends on
+ is the new_target, there is no need for other dependency data.
+
+ update_if_changed() is a micro optimization, resist the temptation to
+ use it in too many places. Only use it when a significant number of
+ files are affected by a change to the target, so the saving in
+ reduced compilation is worth the less readable code in the makefile.
+
hostcc(object_list)
Compile the objects to run on the host system. It uses HOSTCC, the
standard include list, HOSTCFLAGS plus any extra flags for the
@@ -1549,10 +1568,11 @@ CONTROLLING KBUILD
TEMPORARY FILES FOR KBUILD
- All the temporary files and directories create by kbuild start with
- '.tmp_'. Only the kbuild team needs to know what is in these files, but a
- brief list might be useful to the general build audience. This list is
- roughly in the order they appear in the top level and scripts Makefiles.
+ All the temporary files and directories created by kbuild start with
+ '.tmp_' or 'tmp_'. Only the kbuild team needs to know what is in these
+ files, but a brief list might be useful to the general build audience.
+ This list is roughly in the order they appear in the top level and scripts
+ Makefiles.
.tmp_include_list
A shell script which, when executed, returns the external include list,
@@ -1674,6 +1694,11 @@ TEMPORARY FILES FOR KBUILD
fed back into the lexical analyser for macro expansion. It uses this
temporary file for the feedback, the feedback is never more than one
level.
+
+ tmp_<target>
+ Used with update_if_changed() to decide if a file has changed or not.
+ The default for the second parameter of update_if_changed() is the target
+ prefixed with 'tmp_'.
ADDITIONAL TARGETS AND COMMANDS
Index: 13.11/Makefile-2.5
--- 13.11/Makefile-2.5 Mon, 08 Oct 2001 16:39:45 +1000 kaos
(linux-2.4/E/d/40_Makefile-2 1.32 644)
+++ 13.12(w)/Makefile-2.5 Mon, 29 Oct 2001 01:30:33 +1100 kaos
+(linux-2.4/E/d/40_Makefile-2 1.32 644)
@@ -346,6 +346,7 @@ clean: $(KBUILD_OBJTREE).tmp_global_make
-o -name '.SUMS' \
-o -name '.tmp_implicit' \
-o -name '.tmp_*_shipped' \
+ -o -name 'tmp_*' \
-o -size 0 \
\) -type f -print | xargs -r rm -f
$(KBUILD_QUIET)cd $(KBUILD_OBJTREE) && rm -rf $(CLEAN)
Index: 13.11/arch/i386/Makefile.in
--- 13.11/arch/i386/Makefile.in Sat, 06 Oct 2001 15:24:26 +1000 kaos
(linux-2.4/E/d/43_Makefile.i 1.13 644)
+++ 13.12(w)/arch/i386/Makefile.in Mon, 29 Oct 2001 01:33:41 +1100 kaos
+(linux-2.4/E/d/43_Makefile.i 1.13 644)
@@ -12,7 +12,7 @@ extra_aflags(vmlinux.lds.i -no-tradition
# into
# symbol = value /* 0xvalue source */
-user_command(asm-offsets.h
+user_command(tmp_asm-offsets.h
($(objfile asm-offsets.s))
(set -e;
(echo "#ifndef __ASM_OFFSETS_H__";
@@ -41,3 +41,5 @@ user_command(asm-offsets.h
)
()
)
+
+update_if_changed(asm-offsets.h)
Index: 13.11/drivers/scsi/aic7xxx/aicasm/Makefile.in
--- 13.11/drivers/scsi/aic7xxx/aicasm/Makefile.in Wed, 26 Sep 2001 16:51:39 +1000 kaos
(linux-2.4/I/d/38_Makefile.i 1.11 644)
+++ 13.12(w)/drivers/scsi/aic7xxx/aicasm/Makefile.in Mon, 29 Oct 2001 01:29:33 +1100
+kaos (linux-2.4/I/d/38_Makefile.i 1.12 644)
@@ -36,17 +36,15 @@ $(objfile aicasm_scan.lex.o): $(objfile
# which in turn would rebuild aic7xxx EVERY TIME, EVEN IF NOTHING HAD CHANGED!
# Life would be so much easier if aic7xxx used shipped files like everyone else.
-ifeq ($(KBUILD_WRITABLE),y)
- user_command(aicdb.h
+user_command(tmp_aicdb.h
()
(set -e;
- mv -f $@ [email protected] 2>/dev/null || /bin/true;
for inc in db3/db_185.h db2/db_185.h db1/db.h db1/db_185.h db/db.h
db/db_185.h db.h db_185.h ;
do
(echo "#include <$$inc>"; echo "int main(void) { dbopen(\"\", 0, 0, 0, 0);
return(0); }") |
$(HOSTCC) -x c -ldb -o $(objfile .tmp_db3_test) - 2>/dev/null &&
echo "#include <$$inc>" > $@ &&
- (cmp -s $@ [email protected] && mv [email protected] $@ || (rm -f [email protected]; echo " Using `cat
$@` in $@")) &&
+ echo "Using <$$inc> in aicdb.h" &&
break;
done;
rm -f $(objfile .tmp_db3_test);
@@ -57,7 +55,8 @@ ifeq ($(KBUILD_WRITABLE),y)
)
()
)
-endif
+
+update_if_changed(aicdb.h)
$(objfile aicasm_symbol.o): $(objfile aicdb.h)
hostccld(aicasm aicasm.o aicasm_gram.tab.o aicasm_scan.lex.o aicasm_symbol.o)
Index: 13.11/scripts/pp_makefile1_parse.l
--- 13.11/scripts/pp_makefile1_parse.l Thu, 04 Oct 2001 16:53:32 +1000 kaos
(linux-2.4/I/d/31_pp_makefil 1.18 644)
+++ 13.12(w)/scripts/pp_makefile1_parse.l Mon, 29 Oct 2001 01:15:04 +1100 kaos
+(linux-2.4/I/d/31_pp_makefil 1.19 644)
@@ -171,6 +171,10 @@ TRAIL [ \t]*"("
pp_state = 1;
return(BASE_TARGET);
}
+"update_if_changed"/{TRAIL} {
+ pp_state = 1;
+ return(UPDATE_IF_CHANGED);
+ }
"hostcc"/{TRAIL} {
pp_state = 1;
return(HOSTCC);
@@ -548,14 +552,16 @@ void expand_macros(char **is, char **is_
changed = 0;
{
/* Ignore macros in make comments */
- int paren = 0;
+ int paren = 0, dquote = 0;
for (comment = *is; *comment; ++comment) {
- if (*comment == '(') {
+ if (*comment == '(' && !dquote) {
++paren;
- } else if (*comment == ')') {
+ } else if (*comment == ')' && !dquote) {
--paren;
+ } else if (*comment == '"') {
+ dquote = !dquote; /* simplistic, may break on some strings */
} else if (*comment == '#') {
- if (paren == 0 && (comment == *is || *(comment-1) != '\\')) {
+ if (paren == 0 && dquote == 0 && (comment == *is || *(comment-1) != '\\'))
+{
break;
}
}
Index: 13.11/scripts/pp_makefile1_parse.y
--- 13.11/scripts/pp_makefile1_parse.y Thu, 04 Oct 2001 16:53:32 +1000 kaos
(linux-2.4/I/d/35_pp_makefil 1.24 644)
+++ 13.12(w)/scripts/pp_makefile1_parse.y Mon, 29 Oct 2001 01:29:15 +1100 kaos
+(linux-2.4/I/d/35_pp_makefil 1.25 644)
@@ -313,7 +313,7 @@ void y_new_string(char **is, char **is_e
%token EXTRA_CFLAGS EXTRA_CFLAGS_ALL
%token EXTRA_LDFLAGS
%token OBJLINK OBJLINK_COND
-%token USER_COMMAND NODEPEND CREATE_OBJDIR SIDE_EFFECT SHIPPED BASE_TARGET
+%token USER_COMMAND NODEPEND CREATE_OBJDIR SIDE_EFFECT SHIPPED BASE_TARGET
+UPDATE_IF_CHANGED
%token HOSTCC HOSTLD HOSTCCLD
%token SETUP
%token IFSEL IFNSEL IFSELMOD IFSELNMOD
@@ -381,6 +381,7 @@ unit
| side_effect
| shipped
| base_target
+ | update_if_changed
| hostcc
| hostld
| hostccld
@@ -816,6 +817,45 @@ base_target
{ y_printf(")"); }
;
+update_if_changed
+ : UPDATE_IF_CHANGED
+ LPAREN
+ { start_saving_text(); make_target = 0; }
+ local_target
+ optional_any_target
+ RPAREN
+ {
+ char **s, *target1, *target2 = NULL;
+ for (s = saved_text; s && *s; ++s) {
+ if (!isspace(**s)) {
+ target1 = *s;
+ ++s;
+ break;
+ }
+ }
+ for (; s && *s; ++s) {
+ if (!isspace(**s)) {
+ target2 = *s;
+ ++s;
+ break;
+ }
+ }
+ fprintf(yyout, "%s: ", target1+1);
+ if (target2) {
+ fprintf(yyout, " %s\n", target2+1);
+ }
+ else {
+ char *p = strrchr(target1, '/')+1;
+ fprintf(yyout, " %.*stmp_%s\n", p-(target1+1), target1+1, p);
+ }
+ fprintf(yyout, "\t$(KBUILD_QUIET)cmp -s $< $@ || (($(check_writable);) &&
+echo \"Updating $@\" && cp $< $@)\n\n");
+ fprintf(yyout, "# nodepend(%s)\n", target1);
+ do_nodepend(target1);
+ fprintf(yyout, "CLEAN\t+= %s\n", target1+1);
+ free_saved_text(&saved_text);
+ }
+ ;
+
hostcc
: HOSTCC
@@ -1001,6 +1041,11 @@ local_target
}
free($1);
}
+ ;
+
+optional_any_target
+ : any_target
+ | /* empty */
;
any_target_list
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