Re: [PATCH] gas/arc: Allow --with-cpu configure option to change default cpu

[Andrew Burgess <andrew dot burgess at embecosm dot com>]

* Nick Clifton <nickc@redhat.com> [2016-06-28 12:49:16 +0100]:

> Hi Andrew,
> 
> > I see your concern here, however...
> > 
> > If I move the option checking into ARC specific code, but still use
> > AC_ARG_WITH to check for the argument then the help text will always
> > show up for all targets.  Due to our use of AC_DISABLE_OPTION_CHECKING
> > all --with-XXX type options will be accepted by our configure script,
> > and as you point out, when this does not work this might confuse
> > users.
> 
> OK, fair point.
> 
> > What if I changed the current patch to simply remove the help text for
> > the --with-cpu option?
> 
> Well the problem with that is that we now have a silent configuration
> option which only those in the know (or who have actually read the source
> code) will be able to use.
> 
> Instead - how about a compromise:  We go with your original version of
> the patch, but in the help text for the option we specifically mention
> which targets support this option.  (Ie just ARC for now, but extendable
> later on to other targets if they want it).

Hi Nick,

Thanks for your feedback.

I've attached a new revision, this includes NEWS entry, and the help
text that makes it clear the option is only supported on ARC.

Thanks,
Andrew

--

gas/arc: Allow --with-cpu configure option to change default cpu

Add a new configure time option --with-cpu=CPU that can be used to
change the default cpu selection.  Currently this is only supported on
ARC.

If the user specifies --with-cpu=FOO at configure time then the constant
TARGET_WITH_CPU will be defined to "FOO" in config.h, the
TARGET_WITH_CPU constant can then be used in the config/tc-*.c code as a
default string to select an appropriate cpu if the user does not
explicitly select a cpu at gas run-time.

gas/ChangeLog:

	* config.in (TARGET_WITH_CPU): Undefine.
	* configure.ac: Add --with-cpu support, and define in config.h.
	* configure: Regenerate.
	* config/tc-arc.c: Use TARGET_WITH_CPU to select default CPU.
	* NEWS: Mention new configure option.
---
 gas/ChangeLog       |  8 ++++++++
 gas/NEWS            |  3 +++
 gas/config.in       |  3 +++
 gas/config/tc-arc.c |  6 +++++-
 gas/configure       | 18 ++++++++++++++++--
 gas/configure.ac    | 10 ++++++++++
 6 files changed, 45 insertions(+), 3 deletions(-)

diff --git a/gas/NEWS b/gas/NEWS
index 08807f1..d48b097 100644
--- a/gas/NEWS
+++ b/gas/NEWS
@@ -32,6 +32,9 @@
 
 * Add assembly-time relaxation option for ARC cpus.
 
+* Add --with-cpu=TYPE configure option for ARC gas.  This allows the default
+  cpu type to be adjusted at configure time.
+
 Changes in 2.26:
 
 * Add a configure option --enable-compressed-debug-sections={all,gas} to
diff --git a/gas/config.in b/gas/config.in
index e06f160..5129c28 100644
--- a/gas/config.in
+++ b/gas/config.in
@@ -318,6 +318,9 @@
 /* Target vendor. */
 #undef TARGET_VENDOR
 
+/* Target specific CPU. */
+#undef TARGET_WITH_CPU
+
 /* Use b modifier when opening binary files? */
 #undef USE_BINARY_FOPEN
 
diff --git a/gas/config/tc-arc.c b/gas/config/tc-arc.c
index 155d991..d46f593 100644
--- a/gas/config/tc-arc.c
+++ b/gas/config/tc-arc.c
@@ -51,6 +51,10 @@
 /* Equal to MAX_PRECISION in atof-ieee.c.  */
 #define MAX_LITTLENUMS 6
 
+#ifndef TARGET_WITH_CPU
+#define TARGET_WITH_CPU "arc700"
+#endif /* TARGET_WITH_CPU */
+
 /* Enum used to enumerate the relaxable ins operands.  */
 enum rlx_operand_type
 {
@@ -2466,7 +2470,7 @@ md_begin (void)
   const struct arc_opcode *opcode = arc_opcodes;
 
   if (!mach_type_specified_p)
-    arc_select_cpu ("arc700");
+    arc_select_cpu (TARGET_WITH_CPU);
 
   /* The endianness can be chosen "at the factory".  */
   target_big_endian = byte_order == BIG_ENDIAN;
diff --git a/gas/configure b/gas/configure
index b6298b5..00256bf 100755
--- a/gas/configure
+++ b/gas/configure
@@ -771,6 +771,7 @@ enable_x86_relax_relocations
 enable_elf_stt_common
 enable_werror
 enable_build_warnings
+with_cpu
 enable_nls
 enable_maintainer_mode
 with_system_zlib
@@ -1435,6 +1436,7 @@ Optional Packages:
   --with-pic              try to use only PIC/non-PIC objects [default=use
                           both]
   --with-gnu-ld           assume the C compiler uses GNU ld [default=no]
+  --with-cpu=CPU          default cpu variant is CPU (only supported on ARC)
   --with-system-zlib      use installed libz
 
 Some influential environment variables:
@@ -10982,7 +10984,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 10985 "configure"
+#line 10987 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11088,7 +11090,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11091 "configure"
+#line 11093 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11828,6 +11830,13 @@ fi
 ac_config_headers="$ac_config_headers config.h:config.in"
 
 
+
+# Check whether --with-cpu was given.
+if test "${with_cpu+set}" = set; then :
+  withval=$with_cpu;
+fi
+
+
 # PR 14072
 
 
@@ -12870,6 +12879,11 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+cat >>confdefs.h <<_ACEOF
+#define TARGET_WITH_CPU "${with_cpu}"
+_ACEOF
+
+
 for ac_prog in 'bison -y' byacc
 do
   # Extract the first word of "$ac_prog", so it can be a program name with args.
diff --git a/gas/configure.ac b/gas/configure.ac
index 8f71825..7825fc3 100644
--- a/gas/configure.ac
+++ b/gas/configure.ac
@@ -106,6 +106,15 @@ AM_BINUTILS_WARNINGS
 # Generate a header file
 AC_CONFIG_HEADERS(config.h:config.in)
 
+dnl Option --with-cpu=TYPE allows configure type control of the default
+dnl cpu type within the assembler.  Not all targets support this option
+dnl yet, which is why there is no help string, check the code to see if
+dnl your target supports this option.
+AC_ARG_WITH(cpu,
+            AS_HELP_STRING([--with-cpu=CPU],
+            [default cpu variant is CPU (only supported on ARC)]),
+            [],[])
+
 # PR 14072
 AH_VERBATIM([00_CONFIG_H_CHECK],
 [/* Check that config.h is #included before system headers
@@ -780,6 +789,7 @@ AC_DEFINE_UNQUOTED(TARGET_CANONICAL,	"${target}",       [Canonical target.])
 AC_DEFINE_UNQUOTED(TARGET_CPU,		"${target_cpu}",   [Target CPU.])
 AC_DEFINE_UNQUOTED(TARGET_VENDOR,	"${target_vendor}", [Target vendor.])
 AC_DEFINE_UNQUOTED(TARGET_OS,		"${target_os}",    [Target OS.])
+AC_DEFINE_UNQUOTED(TARGET_WITH_CPU,	"${with_cpu}",     [Target specific CPU.])
 
 AC_PROG_YACC
 AM_PROG_LEX
-- 
2.5.1