Since we don't use suffix rules nor implicit rules in gdb, we can
disable them. The advantage is a slightly faster make [1].
Here are some numbers about the speedup. I ran this on my trusty old
Intel Q6600, so the time numbers are probably higher than what you'd get
on any recent hardware. I ran "make" in the gdb/ directory of an
already built repository (configured with --enable-targets=all). I
recorded the time of execution (average of 5). I then ran "make -d" and
recorded the number of printed lines, which gives a rough idea of the
number of operations done.
I compared the following configurations, to see the impact of both the
empty .SUFFIXES target and the empty pattern rules, as well as running
"make -r", which can be considered the "ideal" case.
A - baseline
B - baseline + .SUFFIXES
C - baseline + pattern rules
D - baseline + .SUFFIXES + pattern rules
E - baseline + make -r
config | time (s) | "make -d"
-----------------------------
A | 5.74 | 2396643
B | 1.19 | 298469
C | 2.81 | 1266573
D | 1.13 | 245489
E | 1.01 | 163914
We can see that the empty .SUFFIXES target has a bigger impact than the
empty pattern rules, but still it doesn't hurt to disable the implicit
pattern rules as well.
There are still some mentions of implicit rules I can't get rid of in
the "make -d" output. For example, it's trying to build .c files from
.w files:
Looking for an implicit rule for '/home/simark/src/binutils-gdb/gdb/infrun.c'.
Trying pattern rule with stem 'infrun'.
Trying implicit prerequisite '/home/simark/src/binutils-gdb/gdb/infrun.w'.
and trying to build Makefile.in from a bunch of extensions:
Looking for an implicit rule for 'Makefile.in'.
Trying pattern rule with stem 'Makefile.in'.
Trying implicit prerequisite 'Makefile.in.o'.
Trying pattern rule with stem 'Makefile.in'.
Trying implicit prerequisite 'Makefile.in.c'.
Trying pattern rule with stem 'Makefile.in'.
Trying implicit prerequisite 'Makefile.in.cc'.
... many more ...
If somebody knows how to disable them, we can do it, but at this point
the returns are minimal, so it is not that important.
I verified that both in-tree and out-of-tree builds work.
[1] Switching from explicit rules to pattern rules for files in
subdirectories actually made it slower, so this is kind of a way to
redeem myself. But it the end it's faster than it was previously,
so it was all worth it. :)
gdb/ChangeLog:
* disable-implicit-rules.mk: New file.
* Makefile.in: Include disable-implicit-rules.mk.
* data-directory/Makefile.in: Likewise.
* gnulib/Makefile.in: Likewise.
gdb/doc/ChangeLog:
* Makefile.in: Likewise.
gdb/gdbserver/ChangeLog:
* Makefile.in: Include disable-implicit-rules.mk.
gdb/testsuite/ChangeLog:
* Makefile.in: Include disable-implicit-rules.mk.
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| bfd | ||
| binutils | ||
| config | ||
| cpu | ||
| elfcpp | ||
| etc | ||
| gas | ||
| gdb | ||
| gold | ||
| gprof | ||
| include | ||
| intl | ||
| ld | ||
| libdecnumber | ||
| libiberty | ||
| opcodes | ||
| readline | ||
| sim | ||
| texinfo | ||
| zlib | ||
| .cvsignore | ||
| .gitattributes | ||
| .gitignore | ||
| ChangeLog | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| COPYING.LIB | ||
| COPYING.LIBGLOSS | ||
| COPYING.NEWLIB | ||
| depcomp | ||
| djunpack.bat | ||
| install-sh | ||
| libtool.m4 | ||
| lt~obsolete.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
| ltoptions.m4 | ||
| ltsugar.m4 | ||
| ltversion.m4 | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| makefile.vms | ||
| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| README | ||
| README-maintainer-mode | ||
| setup.com | ||
| src-release.sh | ||
| symlink-tree | ||
| ylwrap | ||
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.