+# forbid_cpu=REGEXP instead of forcing a generic ISA.
+#
+#
+# Terminology
+#
+# Option group or just group:
+# See comment before mips_option_groups.
+#
+# Test options:
+# The options specified in dg-options.
+#
+# Explicit options:
+# The options that were either passed to runtest as "multilib" options
+# (e.g. -mips4 in --target_board=mips-sim-idt/-mips4) or specified as
+# test options. Note that options in parenthesis (i.e. (-mips16)) are
+# not explicit and can be omitted depending on the base options.
+#
+# Base options:
+# Options that are on by default without being specified in dg-options,
+# e.g. -march=mips64r2 for mipsisa64r2-elf or because they've been
+# passed to runtest as "multilib" options.
+#
+# Option array:
+# Many functions in this file work with option arrays. These are
+# two-dimensional Tcl arrays where the first dimension can have three
+# values: option, explicit_p or test_option_p. The second dimension is
+# the name of the option group. "option" contains the name of the
+# option that is in effect from this group. If no option is active it
+# contains the empty string. The flags "explicit_p" and "test_option_p"
+# are set for explicit and test options.