Extend flags to support multibit and enum bitfields.

gdb/ChangeLog:

	Extend flags to support multibit and enum bitfields.
	NEWS: Document new features.
	* c-typeprint.c (c_type_print_varspec_prefix): Handle TYPE_CODE_FLAGS.
	(c_type_print_varspec_suffix, c_type_print_base): Ditto.
	* gdbtypes.c (arch_flags_type): Don't assume all fields are one bit.
	(append_flags_type_field): New function.
	(append_flags_type_flag): Call it.
	* gdbtypes.h (append_flags_type_field): Declare.
	* target-descriptions.c (struct tdesc_type_flag): Delete.
	(enum tdesc_type_kind) <TDESC_TYPE_BOOL>: New enum value.
	(enum tdesc_type_kind) <TDESC_TYPE_ENUM>: Ditto.
	(struct tdesc_type) <u.f>: Delete.
	(tdesc_predefined_types): Add "bool".
	(tdesc_predefined_type): New function.
	(tdesc_gdb_type): Handle TDESC_TYPE_BOOL, TDESC_TYPE_ENUM.
	Update TDESC_TYPE_FLAGS support.
	(tdesc_free_type): Handle TDESC_TYPE_ENUM.  Update TDESC_TYPE_FLAGS.
	(tdesc_create_flags): Update.
	(tdesc_create_enum): New function.
	(tdesc_add_field): Initialize start,end to -1.
	(tdesc_add_typed_bitfield): New function.
	(tdesc_add_bitfield): Call it.
	(tdesc_add_flag): Allow TDESC_TYPE_STRUCT.  Update.
	(tdesc_add_enum_value): New function.
	(maint_print_c_tdesc_cmd): Fold TDESC_TYPE_FLAGS support into
	TDESC_TYPE_STRUCT.  Handle TDESC_TYPE_ENUM.
	* target-descriptions.h (tdesc_create_enum): Declare.
	(tdesc_add_typed_bitfield, tdesc_add_enum_value): Declare.
	* valprint.c (generic_val_print_enum_1): New function.
	(generic_val_print_enum): Call it.
	(val_print_type_code_flags): Make static.  Handle multibit bitfields
	and enum bitfields.
	* valprint.h (val_print_type_code_flags): Delete.
	* xml-tdesc.c (struct tdesc_parsing_data) <current_type_is_flags>:
	Delete.  All uses removed.
	(tdesc_start_enum): New function.
	(tdesc_start_field): Handle multibit and enum bitfields.
	(tdesc_start_enum_value): New function.
	(enum_value_attributes, enum_children, enum_attributes): New static
	globals.
	(feature_children): Add "enum".
	* features/gdb-target.dtd (enum, evalue): New elements.

gdb/doc/ChangeLog:

	* gdb.texinfo (Target Descriptions): New menu item "Enum Target Types".
	(Target Description Format): Mention enum types.  Update docs on
	flags types.
	(Predefined Target Types): Add "bool".
	(Enum Target Types): New node.

gdb/testsuite/ChangeLog:

	* gdb.xml/extra-regs.xml: Add enum, mixed_flags values.
	* gdb.xml/tdesc-regs.exp (load_description): New arg xml_file.
	All callers updated.  Add tests for enums, mixed flags register.

2 files changed, 111 insertions, 22 deletions

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index a48d1c4..c34c4f3 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,11 @@
+2016-03-15  Doug Evans  <dje@google.com>
+
+	* gdb.texinfo (Target Descriptions): New menu item "Enum Target Types".
+	(Target Description Format): Mention enum types.  Update docs on
+	flags types.
+	(Predefined Target Types): Add "bool".
+	(Enum Target Types): New node.
+
 2016-03-15  Pedro Alves  <palves@redhat.com>
 
 	* gdb.texinfo (Tracepoint Actions): Fix typo.
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 71657b0..2f4da84 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -40359,6 +40359,7 @@ target descriptions.  @xref{Expat}.
 * Target Description Format::       The contents of a target description.
 * Predefined Target Types::         Standard types available for target
                                     descriptions.
+* Enum Target Types::               How to define enum target types.
 * Standard Target Features::        Features @value{GDBN} knows about.
 @end menu
 
@@ -40559,7 +40560,8 @@ Any register's value is a collection of bits which @value{GDBN} must
 interpret.  The default interpretation is a two's complement integer,
 but other types can be requested by name in the register description.
 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
-Target Types}), and the description can define additional composite types.
+Target Types}), and the description can define additional composite
+and enum types.
 
 Each type element must have an @samp{id} attribute, which gives
 a unique (within the containing @samp{<feature>}) name to the type.
@@ -40589,46 +40591,84 @@ each of which has a @var{name} and a @var{type}:
 @end smallexample
 
 @cindex <struct>
+@cindex <flags>
 If a register's value is composed from several separate values, define
-it with a structure type.  There are two forms of the @samp{<struct>}
-element; a @samp{<struct>} element must either contain only bitfields
-or contain no bitfields.  If the structure contains only bitfields,
-its total size in bytes must be specified, each bitfield must have an
-explicit start and end, and bitfields are automatically assigned an
-integer type.  The field's @var{start} should be less than or
-equal to its @var{end}, and zero represents the least significant bit.
+it with either a structure type or a flags type.
+A flags type may only contain bitfields.
+A structure type may either contain only bitfields or contain no bitfields.
+If the value contains only bitfields, its total size in bytes must be
+specified.
+
+Non-bitfield values have a @var{name} and @var{type}.
 
 @smallexample
-<struct id="@var{id}" size="@var{size}">
-  <field name="@var{name}" start="@var{start}" end="@var{end}"/>
+<struct id="@var{id}">
+  <field name="@var{name}" type="@var{type}"/>
   @dots{}
 </struct>
 @end smallexample
 
-If the structure contains no bitfields, then each field has an
-explicit type, and no implicit padding is added.
+Both @var{name} and @var{type} values are required.
+No implicit padding is added.
+
+Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
 
 @smallexample
-<struct id="@var{id}">
-  <field name="@var{name}" type="@var{type}"/>
+<struct id="@var{id}" size="@var{size}">
+  <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
   @dots{}
 </struct>
 @end smallexample
 
-@cindex <flags>
-If a register's value is a series of single-bit flags, define it with
-a flags type.  The @samp{<flags>} element has an explicit @var{size}
-and contains one or more @samp{<field>} elements.  Each field has a
-@var{name}, a @var{start}, and an @var{end}.  Only single-bit flags
-are supported.
-
 @smallexample
 <flags id="@var{id}" size="@var{size}">
-  <field name="@var{name}" start="@var{start}" end="@var{end}"/>
+  <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
   @dots{}
 </flags>
 @end smallexample
 
+The @var{name} value is required.
+Bitfield values may be named with the empty string, @samp{""},
+in which case the field is ``filler'' and its value is not printed.
+Not all bits need to be specified, so ``filler'' fields are optional.
+
+The @var{start} value is required, and @var{end} and @var{type}
+are optional.
+The field's @var{start} must be less than or equal to its @var{end},
+and zero represents the least significant bit.
+The default value of @var{end} is @var{start}, a single bit field.
+
+The default value of @var{type} depends on whether the
+@var{end} was specified.  If @var{end} is specified then the default
+value of @var{type} is an unsigned integer.  If @var{end} is unspecified
+then the default value of @var{type} is @code{bool}.
+
+Which to choose?  Structures or flags?
+
+Registers defined with @samp{flags} have these advantages over
+defining them with @samp{struct}:
+
+@itemize @bullet
+@item
+Arithmetic may be performed on them as if they were integers.
+@item
+They are printed in a more readable fashion.
+@end itemize
+
+Registers defined with @samp{struct} have one advantage over
+defining them with @samp{flags}:
+
+@itemize @bullet
+@item
+One can fetch individual fields like in @samp{C}.
+
+@smallexample
+(gdb) print $my_struct_reg.field3
+$1 = 42
+@end smallexample
+
+@end itemize
+
 @subsection Registers
 @cindex <reg>
 
@@ -40697,6 +40737,9 @@ types.  The currently supported types are:
 
 @table @code
 
+@item bool
+Boolean type, occupying a single bit.
+
 @item int8
 @itemx int16
 @itemx int32
@@ -40739,6 +40782,44 @@ The 10-byte extended precision format used by x87 registers.
 
 @end table
 
+@node Enum Target Types
+@section Enum Target Types
+@cindex target descriptions, enum types
+
+Enum target types are useful in @samp{struct} and @samp{flags}
+register descriptions.  @xref{Target Description Format}.
+
+Enum types have a name, size and a list of name/value pairs.
+
+@smallexample
+<enum id="@var{id}" size="@var{size}">
+  <evalue name="@var{name}" value="@var{value}"/>
+  @dots{}
+</enum>
+@end smallexample
+
+Enums must be defined before they are used.
+
+@smallexample
+<enum id="levels_type" size="4">
+  <evalue name="low" value="0"/>
+  <evalue name="high" value="1"/>
+</enum>
+<flags id="flags_type" size="4">
+  <field name="X" start="0"/>
+  <field name="LEVEL" start="1" end="1" type="levels_type"/>
+</flags>
+<reg name="flags" bitsize="32" type="flags_type"/>
+@end smallexample
+
+Given that description, a value of 3 for the @samp{flags} register
+would be printed as:
+
+@smallexample
+(gdb) info register flags
+flags 0x3 [ X LEVEL=high ]
+@end smallexample
+
 @node Standard Target Features
 @section Standard Target Features
 @cindex target descriptions, standard features