rs6000: Improve --help=target (PR85321)

This updates the help text for some options to mention the allowed
values for -mXX=XX.


	PR target/85321
	* config/rs6000/rs6000.opt (mtraceback=): Show the allowed values in
	the help text.
	(mlong-double-): Ditto.
	* config/rs6000/sysv4.opt (msdata=): Ditto.
	(mtls-size=): Ditto.

From-SVN: r259296

gcc/ChangeLog

+2018-04-10  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR target/85321
+	* config/rs6000/rs6000.opt (mtraceback=): Show the allowed values in
+	the help text.
+	(mlong-double-): Ditto.
+	* config/rs6000/sysv4.opt (msdata=): Ditto.
+	(mtls-size=): Ditto.
+
 2018-04-10  Kelvin Nilsen  <kelvin@gcc.gnu.org>
 
 	* config/rs6000/rs6000-c.c (altivec_overloaded_builtins): Remove

gcc/config/rs6000/rs6000.opt

@@ -407,7 +407,7 @@ Target RejectNegative Joined Var(rs6000_tune_index) Init(-1) Enum(rs6000_cpu_opt
 
 mtraceback=
 Target RejectNegative Joined Enum(rs6000_traceback_type) Var(rs6000_traceback)
--mtraceback=	Select full, part, or no traceback table.
+-mtraceback=[full,part,no]	Select type of traceback table.
 
 Enum
 Name(rs6000_traceback_type) Type(enum rs6000_traceback_type)
@@ -435,7 +435,7 @@ Warn about deprecated 'vector long ...' AltiVec type usage.
 
 mlong-double-
 Target RejectNegative Joined UInteger Var(rs6000_long_double_type_size) Save
--mlong-double-<n>	Specify size of long double (64 or 128 bits).
+-mlong-double-[64,128]	Specify size of long double.
 
 ; This option existed in the past, but now is always on.
 mlra

gcc/config/rs6000/sysv4.opt

@@ -25,7 +25,7 @@ Select ABI calling convention.
 
 msdata=
 Target RejectNegative Joined Var(rs6000_sdata_name)
-Select method for sdata handling.
+-msdata=[none,data,sysv,eabi]	Select method for sdata handling.
 
 mreadonly-in-sdata
 Target Report Var(rs6000_readonly_in_sdata) Init(1) Save
@@ -33,7 +33,7 @@ Allow readonly data in sdata.
 
 mtls-size=
 Target RejectNegative Joined Var(rs6000_tls_size) Enum(rs6000_tls_size)
-Specify bit size of immediate TLS offsets.
+-mtls-size=[16,32]	Specify bit size of immediate TLS offsets.
 
 Enum
 Name(rs6000_tls_size) Type(int)