[BUILD] add the CPU=native and ARCH=32/64 build options

Hank A. Paulson suggested to add CPU=native to optimize the code for
the build machine. This makes sense in a lot of situations. Since it
is often possible to have both 32 and 64 bits supported on recent
systems, the ARCH=32 and ARCH=64 build options were also added.

Makefile

@@ -78,14 +78,14 @@ TARGET =
 #### TARGET CPU
 # Use CPU=<cpu_name> to optimize for a particular CPU, among the following
 # list :
-#    generic, i586, i686, ultrasparc, custom
+#    generic, native, i586, i686, ultrasparc, custom
 CPU = generic
 
 #### Architecture, used when not building for native architecture
 # Use ARCH=<arch_name> to force build for a specific architecture. Known
 # architectures will lead to "-m32" or "-m64" being added to CFLAGS and
 # LDFLAGS. This can be required to build 32-bit binaries on 64-bit targets.
-# Currently, only x86_64, i386, i486, i586 and i686 are understood.
+# Currently, only 32, 64, x86_64, i386, i486, i586 and i686 are understood.
 ARCH =
 
 #### Toolchain options.
@@ -134,12 +134,15 @@ SILENT_DEFINE =
 # them. You should not have to change these options. Better use CPU_CFLAGS or
 # even CFLAGS instead.
 CPU_CFLAGS.generic    = -O2
+CPU_CFLAGS.native     = -O2 -march=native
 CPU_CFLAGS.i586       = -O2 -march=i586
 CPU_CFLAGS.i686       = -O2 -march=i686
 CPU_CFLAGS.ultrasparc = -O6 -mcpu=v9 -mtune=ultrasparc
 CPU_CFLAGS            = $(CPU_CFLAGS.$(CPU))
 
 #### ARCH dependant flags, may be overriden by CPU flags
+ARCH_FLAGS.32     = -m32
+ARCH_FLAGS.64     = -m64
 ARCH_FLAGS.i386   = -m32 -march=i386
 ARCH_FLAGS.i486   = -m32 -march=i486
 ARCH_FLAGS.i586   = -m32 -march=i586

Makefile.bsd

@@ -13,6 +13,7 @@ TARGET = openbsd
 
 # pass CPU=<cpu_name> to make to optimize for a particular CPU
 CPU = generic
+#CPU = native
 #CPU = i586
 #CPU = i686
 #CPU = ultrasparc
@@ -37,6 +38,7 @@ LIBS.openbsd =
 
 # CPU dependant optimizations
 COPTS.generic = -O2
+COPTS.native = -O2 -march=native
 COPTS.i586 = -O2 -march=i586
 COPTS.i686 = -O2 -march=i686
 COPTS.ultrasparc = -O6 -mcpu=v9 -mtune=ultrasparc

Makefile.osx

@@ -13,6 +13,7 @@ TARGET = generic
 
 # pass CPU=<cpu_name> to make to optimize for a particular CPU
 CPU = generic
+#CPU = native
 #CPU = i586
 #CPU = i686
 #CPU = ultrasparc
@@ -40,6 +41,7 @@ LIBS.darwin =
 
 # CPU dependant optimizations
 COPTS.generic = -O2
+COPTS.native = -O2 -march=native
 COPTS.i586 = -O2 -march=i586
 COPTS.i686 = -O2 -march=i686
 COPTS.ultrasparc = -O6 -mcpu=v9 -mtune=ultrasparc

README

@@ -39,6 +39,7 @@ one of the following choices to the CPU variable :
   - i686 for intel PentiumPro, Pentium 2 and above, AMD Athlon
   - i586 for intel Pentium, AMD K6, VIA C3.
   - ultrasparc : Sun UltraSparc I/II/III/IV processor
+  - native : use the build machine's specific processor optimizations
   - generic : any other processor or no specific optimization. (default)
 
 Alternatively, you may just set the CPU_CFLAGS value to the optimal GCC options
@@ -47,8 +48,8 @@ for your platform.
 You may want to build specific target binaries which do not match your native
 compiler's target. This is particularly true on 64-bit systems when you want
 to build a 32-bit binary. Use the ARCH variable for this purpose. Right now
-it only knows about a few x86 variants (i386,i486,i586,i686,x86_64) and sets
+it only knows about a few x86 variants (i386,i486,i586,i686,x86_64), two
--m32/-m64 as well as -march=<arch> accordingly.
+generic ones (32,64) and sets -m32/-m64 as well as -march=<arch> accordingly.
 
 If your system supports PCRE (Perl Compatible Regular Expressions), then you
 really should build with libpcre which is between 2 and 10 times faster than