Commonise tdesc_reg and makes use of it in gdbserver tdesc

gdb/
	* Makefile.in: Add arch/tdesc.c
	* common/tdesc.c: New file.
	* common/tdesc.h (tdesc_element_visitor): Move to here.
	(tdesc_element): Likewise.
	(tdesc_reg): Likewise.
	(tdesc_reg_up): Likewise.
	* regformats/regdef.h (reg): Add offset to constructors.
	* target-descriptions.c (tdesc_element_visitor): Move from here.
	(tdesc_element): Likewise.
	(tdesc_reg): Likewise.
	(tdesc_reg_up): Likewise.

gdbserver/
	* Makefile.in: Add common/tdesc.c
	* tdesc.c (init_target_desc): init all reg_defs from register vector.
	(tdesc_create_reg): Create tdesc_reg.
	* tdesc.h (tdesc_feature): Add register vector.

4 files changed, 30 insertions, 9 deletions

diff --git a/gdb/gdbserver/ChangeLog b/gdb/gdbserver/ChangeLog
index 8e0f13a..29355bb 100644
--- a/gdb/gdbserver/ChangeLog
+++ b/gdb/gdbserver/ChangeLog
@@ -1,3 +1,11 @@
+2018-04-18  Alan Hayward  <alan.hayward@arm.com>
+
+	* Makefile.in: Add common/tdesc.c
+	* tdesc.c (init_target_desc): init all reg_defs from register
+	vector.
+	(tdesc_create_reg): Create tdesc_reg.
+	* tdesc.h (tdesc_feature): Add register vector.
+
 2018-03-30  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	* tdesc.h (struct target_desc) <features>: Change type to
diff --git a/gdb/gdbserver/Makefile.in b/gdb/gdbserver/Makefile.in
index 75fbf7e..4a54235 100644
--- a/gdb/gdbserver/Makefile.in
+++ b/gdb/gdbserver/Makefile.in
@@ -215,6 +215,7 @@ SFILES = \
 	$(srcdir)/common/print-utils.c \
 	$(srcdir)/common/ptid.c \
 	$(srcdir)/common/rsp-low.c \
+	$(srcdir)/common/tdesc.c \
 	$(srcdir)/common/vec.c \
 	$(srcdir)/common/xml-utils.c \
 	$(srcdir)/nat/linux-btrace.c \
@@ -258,6 +259,7 @@ OBS = \
 	common/rsp-low.o \
 	common/signals.o \
 	common/signals-state-save-restore.o \
+	common/tdesc.o \
 	common/vec.o \
 	common/xml-utils.o \
 	debug.o \
@@ -403,6 +405,7 @@ IPA_OBJS = \
 	common/format-ipa.o \
 	common/print-utils-ipa.o \
 	common/rsp-low-ipa.o \
+	common/tdesc-ipa.o \
 	common/vec-ipa.o \
 	regcache-ipa.o \
 	remote-utils-ipa.o \
diff --git a/gdb/gdbserver/tdesc.c b/gdb/gdbserver/tdesc.c
index 9f00ecf..afe0187 100644
--- a/gdb/gdbserver/tdesc.c
+++ b/gdb/gdbserver/tdesc.c
@@ -54,10 +54,19 @@ init_target_desc (struct target_desc *tdesc)
 {
   int offset = 0;
 
-  for (reg &reg : tdesc->reg_defs)
+  /* Go through all the features and populate reg_defs.  */
+  for (const tdesc_reg_up &treg : tdesc->registers)
     {
-      reg.offset = offset;
-      offset += reg.size;
+      int regnum = treg->target_regnum;
+
+      /* Register number will increase (possibly with gaps) or be zero.  */
+      gdb_assert (regnum == 0 || regnum >= tdesc->reg_defs.size ());
+
+      if (regnum != 0)
+	tdesc->reg_defs.resize (regnum, reg (offset));
+
+      tdesc->reg_defs.emplace_back (treg->name.c_str (), offset, treg->bitsize);
+      offset += treg->bitsize;
     }
 
   tdesc->registers_size = offset / 8;
@@ -222,12 +231,10 @@ tdesc_create_reg (struct tdesc_feature *feature, const char *name,
 {
   struct target_desc *tdesc = (struct target_desc *) feature;
 
-  gdb_assert (regnum == 0 || regnum >= tdesc->reg_defs.size ());
-
-  if (regnum != 0)
-    tdesc->reg_defs.resize (regnum);
+  tdesc_reg *reg = new tdesc_reg (feature, name, regnum, save_restore,
+				  group, bitsize, type);
 
-  tdesc->reg_defs.emplace_back (name, bitsize);
+  tdesc->registers.emplace_back (reg);
 }
 
 /* See common/tdesc.h.  */
diff --git a/gdb/gdbserver/tdesc.h b/gdb/gdbserver/tdesc.h
index 85139d9..8eb88ee 100644
--- a/gdb/gdbserver/tdesc.h
+++ b/gdb/gdbserver/tdesc.h
@@ -25,7 +25,10 @@
 #include <vector>
 
 struct tdesc_feature
-{};
+{
+  /* The registers associated with this feature.  */
+  std::vector<tdesc_reg_up> registers;
+};
 
 /* A target description.  Inherit from tdesc_feature so that target_desc
    can be used as tdesc_feature.  */