tdesc: handle arbitrary strings in tdesc_register_in_reggroup_p

tdesc_register_in_reggroup_p in now able to handle arbitrary
groups. This is useful when groups are created while the
target descriptor file is received from the remote.

This can be the case of a soft core target processor where
registers/groups can change.

gdb/ChangeLog:

yyyy-mm-dd  Franck Jullien  <franck.jullien@gmail.com>
	    Stafford Horne  <shorne@gmail.com>

	* target-descriptions.c (tdesc_register_in_reggroup_p): Support
	arbitrary strings.
	(tdesc_use_registers): Add logic to register new reggroups.
	(tdesc_reg::group): Update comment to indicate we allow
	arbitrary strings.
	* NEWS (Changes since GDB 8.0): Announce that GDB supports
	arbitrary reggroups.

gdb/testsuite/ChangeLog:

yyyy-mm-dd  Stafford Horne  <shorne@gmail.com>

	* gdb.xml/extra-regs.xml: Add example foo reggroup.
	* gdb.xml/tdesc-regs.exp: Add test to check for foo reggroup.

gdb/doc/ChangeLog:

yyyy-mm-dd  Stafford Horne  <shorne@gmail.com>

	* gdb.texinfo (Target Description Format): Explain that arbitrary
	strings are now allowed for register groups.

8 files changed, 57 insertions, 41 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e3ef0fe5d9..4d85029b99 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,14 @@
+2017-12-27  Franck Jullien  <franck.jullien@gmail.com>
+	    Stafford Horne  <shorne@gmail.com>
+
+	* target-descriptions.c (tdesc_register_in_reggroup_p): Support
+	arbitrary strings.
+	(tdesc_use_registers): Add logic to register new reggroups.
+	(tdesc_reg::group): Update comment to indicate we allow
+	arbitrary strings.
+	* NEWS (Changes since GDB 8.0): Announce that GDB supports
+	arbitrary reggroups.
+
 2017-12-27  Stafford Horne  <shorne@gmail.com>
 
 	* reggroups.c (reggroup_gdbarch_new): New function.
diff --git a/gdb/NEWS b/gdb/NEWS
index 44f481d1f5..c861853798 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,10 @@
 
 *** Changes since GDB 8.0
 
+* GDB now supports dynamically creating arbitrary register groups specified
+  in XML target descriptions.  This allows for finer grain grouping of
+  registers on systems with a large amount of registers.
+
 * The 'ptype' command now accepts a '/o' flag, which prints the
   offsets and sizes of fields in a struct, like the pahole(1) tool.
 
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index e958c23d88..6a0dbda51e 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,5 +1,10 @@
 2017-12-27  Stafford Horne  <shorne@gmail.com>
 
+	* gdb.texinfo (Target Description Format): Explain that arbitrary
+	strings are now allowed for register groups.
+
+2017-12-27  Stafford Horne  <shorne@gmail.com>
+
 	* gdb.texinfo (Registers): Document info reg $reggroup feature.
 
 2017-12-15  Sergio Durigan Junior  <sergiodj@redhat.com>
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index a16e79bc2a..f8ecf216b4 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -41761,10 +41761,13 @@ architecture's normal floating point format) of the correct size for
 @var{bitsize}.  The default is @code{int}.
 
 @item group
-The register group to which this register belongs.  It must
-be either @code{general}, @code{float}, or @code{vector}.  If no
-@var{group} is specified, @value{GDBN} will not display the register
-in @code{info registers}.
+The register group to which this register belongs.  It can be one of the
+standard register groups @code{general}, @code{float}, @code{vector} or an
+arbitrary string.  Group names should be limited to alphanumeric characters.
+If a group name is made up of multiple words the words may be separated by
+hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}.  If no
+@var{group} is specified, @value{GDBN} will not display the register in
+@code{info registers}.
 
 @end table
 
diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index b37f4f0c19..e8f098e09e 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -111,12 +111,11 @@ struct tdesc_reg : tdesc_element
   int save_restore;
 
   /* The name of the register group containing this register, or empty
-     if the group should be automatically determined from the
-     register's type.  If this is "general", "float", or "vector", the
-     corresponding "info" command should display this register's
-     value.  It can be an arbitrary string, but should be limited to
-     alphanumeric characters and internal hyphens.  Currently other
-     strings are ignored (treated as empty).  */
+     if the group should be automatically determined from the register's
+     type.  This is traditionally "general", "float", "vector" but can
+     also be an arbitrary string.  If defined the corresponding "info"
+     command should display this register's value.  The string should be
+     limited to alphanumeric characters and internal hyphens.  */
   std::string group;
 
   /* The size of the register, in bits.  */
@@ -1279,17 +1278,13 @@ tdesc_remote_register_number (struct gdbarch *gdbarch, int regno)
 }
 
 /* Check whether REGNUM is a member of REGGROUP.  Registers from the
-   target description may be classified as general, float, or vector.
-   Unlike a gdbarch register_reggroup_p method, this function will
-   return -1 if it does not know; the caller should handle registers
-   with no specified group.
-
-   Arbitrary strings (other than "general", "float", and "vector")
-   from the description are not used; they cause the register to be
-   displayed in "info all-registers" but excluded from "info
-   registers" et al.  The names of containing features are also not
-   used.  This might be extended to display registers in some more
-   useful groupings.
+   target description may be classified as general, float, vector or other
+   register groups registered with reggroup_add().  Unlike a gdbarch
+   register_reggroup_p method, this function will return -1 if it does not
+   know; the caller should handle registers with no specified group.
+
+   The names of containing features are not used.  This might be extended
+   to display registers in some more useful groupings.
 
    The save-restore flag is also implemented here.  */
 
@@ -1299,26 +1294,9 @@ tdesc_register_in_reggroup_p (struct gdbarch *gdbarch, int regno,
 {
   struct tdesc_reg *reg = tdesc_find_register (gdbarch, regno);
 
-  if (reg != NULL && !reg->group.empty ())
-    {
-      int general_p = 0, float_p = 0, vector_p = 0;
-
-      if (reg->group == "general")
-	general_p = 1;
-      else if (reg->group == "float")
-	float_p = 1;
-      else if (reg->group == "vector")
-	vector_p = 1;
-
-      if (reggroup == float_reggroup)
-	return float_p;
-
-      if (reggroup == vector_reggroup)
-	return vector_p;
-
-      if (reggroup == general_reggroup)
-	return general_p;
-    }
+  if (reg != NULL && !reg->group.empty ()
+      && (reg->group == reggroup_name (reggroup)))
+	return 1;
 
   if (reg != NULL
       && (reggroup == save_reggroup || reggroup == restore_reggroup))
@@ -1421,6 +1399,12 @@ tdesc_use_registers (struct gdbarch *gdbarch,
 	void **slot = htab_find_slot (reg_hash, reg.get (), INSERT);
 
 	*slot = reg.get ();
+	/* Add reggroup if its new.  */
+	if (!reg->group.empty ())
+	  if (reggroup_find (gdbarch, reg->group.c_str ()) == NULL)
+	    reggroup_add (gdbarch, reggroup_gdbarch_new (gdbarch,
+							 reg->group.c_str (),
+							 USER_REGGROUP));
       }
 
   /* Remove any registers which were assigned numbers by the
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 4f708f0bfe..e3f18aeeea 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,10 @@
 2017-12-27  Stafford Horne  <shorne@gmail.com>
 
+	* gdb.xml/extra-regs.xml: Add example foo reggroup.
+	* gdb.xml/tdesc-regs.exp: Add test to check for foo reggroup.
+
+2017-12-27  Stafford Horne  <shorne@gmail.com>
+
 	* gdb.base/reggroups.c: New file.
 	* gdb.base/reggroups.exp: New file.
 
diff --git a/gdb/testsuite/gdb.xml/extra-regs.xml b/gdb/testsuite/gdb.xml/extra-regs.xml
index 997d6598e5..302e64ce7d 100644
--- a/gdb/testsuite/gdb.xml/extra-regs.xml
+++ b/gdb/testsuite/gdb.xml/extra-regs.xml
@@ -53,5 +53,6 @@
     <reg name="bitfields" bitsize="64" type="struct2"/>
     <reg name="flags" bitsize="32" type="flags"/>
     <reg name="mixed_flags" bitsize="32" type="mixed_flags"/>
+    <reg name="groupreg" bitsize="32" type="uint32" group="foo"/>
   </feature>
 </target>
diff --git a/gdb/testsuite/gdb.xml/tdesc-regs.exp b/gdb/testsuite/gdb.xml/tdesc-regs.exp
index d62ed9841b..e8b7fd506b 100644
--- a/gdb/testsuite/gdb.xml/tdesc-regs.exp
+++ b/gdb/testsuite/gdb.xml/tdesc-regs.exp
@@ -190,6 +190,9 @@ gdb_test "ptype \$flags" \
     "type = flag flags {\r\n *bool X @0;\r\n *uint32_t Y @2;\r\n}"
 gdb_test "ptype \$mixed_flags" \
     "type = flag mixed_flags {\r\n *bool A @0;\r\n *uint32_t B @1-3;\r\n *bool C @4;\r\n *uint32_t D @5;\r\n *uint32_t @6-7;\r\n *enum {yes = 1, no = 0, maybe = 2, so} Z @8-9;\r\n}"
+# Reggroups should have at least general and the extra foo group
+gdb_test "maintenance print reggroups" \
+    " Group\[ \t\]+Type\[ \t\]+\r\n.* general\[ \t\]+user\[ \t\]+\r\n.* foo\[ \t\]+user\[ \t\]+"
 
 load_description "core-only.xml" "" "test-regs.xml"
 # The extra register from the previous description should be gone.