rs6000: Add -mdejagnu-cpu=

This adds an option -mdejagnu-cpu=.  This option simply overrides what
is given in -mcpu=.  The reason for this is that with older versions
of DejaGnu the value given in the RUNTESTFLAGS will override the value
a testcase wants to have.


	* config/rs6000/rs6000.c (rs6000_option_override_internal): If
	rs6000_dejagnu_cpu_index is set, use that to override rs6000_cpu_index.
	* config/rs6000/rs6000.opt (mdejagnu-cpu=): New option.

From-SVN: r269322

gcc/ChangeLog

+2019-03-01  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	* config/rs6000/rs6000.c (rs6000_option_override_internal): If
+	rs6000_dejagnu_cpu_index is set, use that to override rs6000_cpu_index.
+	* config/rs6000/rs6000.opt (mdejagnu-cpu=): New option.
+
 2019-03-01  Alexander Monakov  <amonakov@ispras.ru>
 
 	PR rtl-optimization/85899

gcc/config/rs6000/rs6000.c

@@ -3869,6 +3869,9 @@ rs6000_option_override_internal (bool global_init_p)
   /* Don't override by the processor default if given explicitly.  */
   set_masks &= ~rs6000_isa_flags_explicit;
 
+  if (global_init_p && rs6000_dejagnu_cpu_index >= 0)
+    rs6000_cpu_index = rs6000_dejagnu_cpu_index;
+
   /* Process the -mcpu=<xxx> and -mtune=<xxx> argument.  If the user changed
      the cpu in a target attribute or pragma, but did not specify a tuning
      option, use the cpu for the tuning option rather than the option specified

gcc/config/rs6000/rs6000.opt

@@ -385,6 +385,13 @@ mtune=
 Target RejectNegative Joined Var(rs6000_tune_index) Init(-1) Enum(rs6000_cpu_opt_value) Save
 -mtune=	Schedule code for given CPU.
 
+; Only for use in the testsuite.  This simply overrides -mcpu=.  With older
+; versions of Dejagnu the command line arguments you set in RUNTESTFLAGS
+; override those set in the testcases; with this option, the testcase will
+; always win.
+mdejagnu-cpu=
+Target Undocumented RejectNegative Joined Var(rs6000_dejagnu_cpu_index) Init(-1) Enum(rs6000_cpu_opt_value) Save
+
 mtraceback=
 Target RejectNegative Joined Enum(rs6000_traceback_type) Var(rs6000_traceback)
 -mtraceback=[full,part,no]	Select type of traceback table.