[PATCH] Have regdat.sh always rewrite the output register file

[Patrick Palka <patrick at parcs dot ath dot cx>]

The rules for generating the output register files look like:

amd64.c : $(srcdir)/../regformats/i386/amd64.dat $(regdat_sh)
	$(SHELL) $(regdat_sh) $(srcdir)/../regformats/i386/amd64.dat amd64.c

According to this rule, if regdat.sh is newer than amd64.c, then
regdat.sh shall be invoked on amd64.dat.  According to regdat.sh, if the
script determines that the output file amd64.c has not changed, then it
will not overwrite the existing output file.  This means that a
subsequent invocation of make will trigger the above rule again as
regdat.sh will be perpetually newer than amd64.c.

This then shows up in the make output like so:

/bin/bash ./../regformats/regdat.sh ./../regformats/i386/amd64-linux.dat amd64-linux.c
amd64-linux.c unchanged.
/bin/bash ./../regformats/regdat.sh ./../regformats/i386/amd64-avx-linux.dat amd64-avx-linux.c
amd64-avx-linux.c unchanged.
...

To fix this pathological behavior, it suffices to have regdat.sh
unconditionally rewrite the output register file.

On my machine, which has a regdat.sh file that is newer than some of the
input register files, this change speeds up every invocation of make
under gdb/ by about 5 seconds.
---
 gdb/ChangeLog            |  4 ++++
 gdb/regformats/regdat.sh | 14 +-------------
 2 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e878efa..cdd6616 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2014-01-10  Patrick Palka  <patrick@parcs.ath.cx>
+
+	* regformats/regdat.sh: Always rewrite the register file.
+
 2014-01-02  Patrick Palka  <patrick@parcs.ath.cx>
 
 	PR gdb/16120
diff --git a/gdb/regformats/regdat.sh b/gdb/regformats/regdat.sh
index 0cf4588..fabc910 100755
--- a/gdb/regformats/regdat.sh
+++ b/gdb/regformats/regdat.sh
@@ -18,18 +18,6 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-move_if_change ()
-{
-    file=$1
-    if test -r ${file} && cmp -s "${file}" new-"${file}"
-    then
-	echo "${file} unchanged." 1>&2
-    else
-	mv new-"${file}" "${file}"
-	echo "${file} updated." 1>&2
-    fi
-}
-
 # Format of the input files
 read="type entry"
 
@@ -202,4 +190,4 @@ EOF
 
 # close things off
 exec 1>&2
-move_if_change $2
+mv -- "new-$2" "$2"
-- 
1.8.5.2