Generate c for feature instead of tdesc

This patch changes Makefile and command "maint print c-files" so
that GDB can print c files for features instead target description.
Previously, we feed GDB a target description xml file, which generate
c files including multiple features.

With this patch, in Makefile, we wrap each feature xml file, and
create a temp target description which include only one feature.
Then, adjust the target description printer for them, and print
a c function for each given feature, so that we can use these
c functions later to create target description in a flexible way.

Before GDB prints c-tdesc, we need to set tdesc.  However, this involves
some validations in each gdbarch on these target descriptions, and this
make troubles to generate c file for each target feature when we feed GDB
a target description only including an optional feature (without some
mandatory feature), GDB just reject it, and don't print the c file.

What we need here is to translate xml file to object target_desc, and
translate the object target_desc to c file.  We don't have to involve
gdbarch validation in this process at all, so I modify command
"maint print c-tdesc" to have an optional argument which is the filename
of xml target description.  If the file name is provided, parse the
xml target description, create target_desc object, and print c file from
it.

gdb:

2017-05-22  Yao Qi  <yao.qi@linaro.org>

	* features/Makefile (FEATURE_XMLFILES): New.
	(FEATURE_CFILES): New.
	New rules.
	* features/i386/32bit-avx.c: Generated.
 	* features/i386/32bit-avx512.c: Generated.
 	* features/i386/32bit-core.c: Generated.
 	* features/i386/32bit-linux.c: Generated.
 	* features/i386/32bit-mpx.c: Generated.
 	* features/i386/32bit-pkeys.c: Generated.
 	* features/i386/32bit-sse.c: Generated.
 	* target-descriptions.c: Include algorithm.
	(tdesc_element_visitor): Add method visit_end.
	(print_c_tdesc): Implement visit_end.
	(print_c_tdesc:: m_filename_after_features): Move it to
	protected.
	(print_c_feature): New class.
	(maint_print_c_tdesc_cmd): Use print_c_feature if XML file
	name starts with "i386/32bit-".

gdb/doc:

2017-06-08  Yao Qi  <yao.qi@linaro.org>

	* gdb.texinfo (Maintenance Commands): Document optional
	argument of "maint print c-tdesc".

10 files changed, 425 insertions, 17 deletions

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index c167a86..b78d8ac 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -34687,11 +34687,13 @@ checksum.
 Print the entire architecture configuration.  The optional argument
 @var{file} names the file where the output goes.
 
-@kindex maint print c-tdesc
+@kindex maint print c-tdesc @r{[}@var{file}@r{]}
 @item maint print c-tdesc
-Print the current target description (@pxref{Target Descriptions}) as
-a C source file.  The created source file can be used in @value{GDBN}
-when an XML parser is not available to parse the description.
+Print the target description (@pxref{Target Descriptions}) as
+a C source file.  The target description is got from the optional
+argument @var{file} or the current target description.  The created
+source file can be used in @value{GDBN} when an XML parser is not
+available to parse the description.
 
 @kindex maint print dummy-frames
 @item maint print dummy-frames
diff --git a/gdb/features/Makefile b/gdb/features/Makefile
index 3bc8b5a..28a7e20 100644
--- a/gdb/features/Makefile
+++ b/gdb/features/Makefile
@@ -252,12 +252,39 @@ $(outdir)/%.dat: %.xml number-regs.xsl sort-regs.xsl gdbserver-regs.xsl
 	  $(XSLTPROC) gdbserver-regs.xsl - >> $(outdir)/$*.tmp
 	sh ../../move-if-change $(outdir)/$*.tmp $(outdir)/$*.dat
 
-cfiles: $(CFILES)
-%.c: %.xml
+FEATURE_XMLFILES = i386/32bit-core.xml \
+	i386/32bit-sse.xml \
+	i386/32bit-linux.xml \
+	i386/32bit-avx.xml \
+	i386/32bit-mpx.xml \
+	i386/32bit-avx512.xml \
+	i386/32bit-pkeys.xml
+
+FEATURE_CFILES = $(patsubst %.xml,%.c,$(FEATURE_XMLFILES))
+
+cfiles: $(CFILES) $(FEATURE_CFILES)
+
+$(CFILES): %.c: %.xml
 	$(GDB) -nx -q -batch \
 	  -ex "set tdesc filename $<" -ex 'maint print c-tdesc' > $@.tmp
 	sh ../../move-if-change $@.tmp $@
 
+$(FEATURE_CFILES): %.c: %.xml.tmp
+	$(GDB) -nx -q -batch \
+	  -ex 'maint print c-tdesc $<' > $@.tmp
+	sh ../../move-if-change $@.tmp $@
+	rm $<
+
+%.xml.tmp: %.xml
+	echo "<?xml version=\"1.0\"?>" > $@
+	echo "<!DOCTYPE target SYSTEM \"gdb-target.dtd\">" >> $@
+	echo "<target>" >> $@
+	echo "  <architecture>" >> $@
+	if test $(findstring i386/32bit-,$@); then echo "i386" >> $@ ; fi;
+	echo "  </architecture>" >> $@
+	echo "  <xi:include href=\"$(notdir $<)\"/>" >> $@
+	echo "</target>" >> $@
+
 # Other dependencies.
 $(outdir)/arm/arm-with-iwmmxt.dat: arm/arm-core.xml arm/xscale-iwmmxt.xml
 $(outdir)/i386/i386.dat: i386/32bit-core.xml i386/32bit-sse.xml
diff --git a/gdb/features/i386/32bit-avx.c b/gdb/features/i386/32bit-avx.c
new file mode 100644
index 0000000..53a939b
--- /dev/null
+++ b/gdb/features/i386/32bit-avx.c
@@ -0,0 +1,23 @@
+/* THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi:set ro:
+  Original: 32bit-avx.xml.tmp */
+
+#include "defs.h"
+#include "osabi.h"
+#include "target-descriptions.h"
+
+static int
+create_feature_i386_32bit_avx (struct target_desc *result, long regnum)
+{
+  struct tdesc_feature *feature;
+
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx");
+  tdesc_create_reg (feature, "ymm0h", regnum++, 1, NULL, 128, "uint128");
+  tdesc_create_reg (feature, "ymm1h", regnum++, 1, NULL, 128, "uint128");
+  tdesc_create_reg (feature, "ymm2h", regnum++, 1, NULL, 128, "uint128");
+  tdesc_create_reg (feature, "ymm3h", regnum++, 1, NULL, 128, "uint128");
+  tdesc_create_reg (feature, "ymm4h", regnum++, 1, NULL, 128, "uint128");
+  tdesc_create_reg (feature, "ymm5h", regnum++, 1, NULL, 128, "uint128");
+  tdesc_create_reg (feature, "ymm6h", regnum++, 1, NULL, 128, "uint128");
+  tdesc_create_reg (feature, "ymm7h", regnum++, 1, NULL, 128, "uint128");
+  return regnum;
+}
diff --git a/gdb/features/i386/32bit-avx512.c b/gdb/features/i386/32bit-avx512.c
new file mode 100644
index 0000000..9bbf392
--- /dev/null
+++ b/gdb/features/i386/32bit-avx512.c
@@ -0,0 +1,35 @@
+/* THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi:set ro:
+  Original: 32bit-avx512.xml.tmp */
+
+#include "defs.h"
+#include "osabi.h"
+#include "target-descriptions.h"
+
+static int
+create_feature_i386_32bit_avx512 (struct target_desc *result, long regnum)
+{
+  struct tdesc_feature *feature;
+
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.avx512");
+  struct tdesc_type *field_type;
+  field_type = tdesc_named_type (feature, "uint128");
+  tdesc_create_vector (feature, "v2ui128", field_type, 2);
+
+  tdesc_create_reg (feature, "k0", regnum++, 1, NULL, 64, "uint64");
+  tdesc_create_reg (feature, "k1", regnum++, 1, NULL, 64, "uint64");
+  tdesc_create_reg (feature, "k2", regnum++, 1, NULL, 64, "uint64");
+  tdesc_create_reg (feature, "k3", regnum++, 1, NULL, 64, "uint64");
+  tdesc_create_reg (feature, "k4", regnum++, 1, NULL, 64, "uint64");
+  tdesc_create_reg (feature, "k5", regnum++, 1, NULL, 64, "uint64");
+  tdesc_create_reg (feature, "k6", regnum++, 1, NULL, 64, "uint64");
+  tdesc_create_reg (feature, "k7", regnum++, 1, NULL, 64, "uint64");
+  tdesc_create_reg (feature, "zmm0h", regnum++, 1, NULL, 256, "v2ui128");
+  tdesc_create_reg (feature, "zmm1h", regnum++, 1, NULL, 256, "v2ui128");
+  tdesc_create_reg (feature, "zmm2h", regnum++, 1, NULL, 256, "v2ui128");
+  tdesc_create_reg (feature, "zmm3h", regnum++, 1, NULL, 256, "v2ui128");
+  tdesc_create_reg (feature, "zmm4h", regnum++, 1, NULL, 256, "v2ui128");
+  tdesc_create_reg (feature, "zmm5h", regnum++, 1, NULL, 256, "v2ui128");
+  tdesc_create_reg (feature, "zmm6h", regnum++, 1, NULL, 256, "v2ui128");
+  tdesc_create_reg (feature, "zmm7h", regnum++, 1, NULL, 256, "v2ui128");
+  return regnum;
+}
diff --git a/gdb/features/i386/32bit-core.c b/gdb/features/i386/32bit-core.c
new file mode 100644
index 0000000..c5f0fca
--- /dev/null
+++ b/gdb/features/i386/32bit-core.c
@@ -0,0 +1,68 @@
+/* THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi:set ro:
+  Original: 32bit-core.xml.tmp */
+
+#include "defs.h"
+#include "osabi.h"
+#include "target-descriptions.h"
+
+static int
+create_feature_i386_32bit_core (struct target_desc *result, long regnum)
+{
+  struct tdesc_feature *feature;
+
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core");
+  struct tdesc_type *field_type;
+  struct tdesc_type *type;
+  type = tdesc_create_flags (feature, "i386_eflags", 4);
+  tdesc_add_flag (type, 0, "CF");
+  tdesc_add_flag (type, 1, "");
+  tdesc_add_flag (type, 2, "PF");
+  tdesc_add_flag (type, 4, "AF");
+  tdesc_add_flag (type, 6, "ZF");
+  tdesc_add_flag (type, 7, "SF");
+  tdesc_add_flag (type, 8, "TF");
+  tdesc_add_flag (type, 9, "IF");
+  tdesc_add_flag (type, 10, "DF");
+  tdesc_add_flag (type, 11, "OF");
+  tdesc_add_flag (type, 14, "NT");
+  tdesc_add_flag (type, 16, "RF");
+  tdesc_add_flag (type, 17, "VM");
+  tdesc_add_flag (type, 18, "AC");
+  tdesc_add_flag (type, 19, "VIF");
+  tdesc_add_flag (type, 20, "VIP");
+  tdesc_add_flag (type, 21, "ID");
+
+  tdesc_create_reg (feature, "eax", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "ecx", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "edx", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "ebx", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "esp", regnum++, 1, NULL, 32, "data_ptr");
+  tdesc_create_reg (feature, "ebp", regnum++, 1, NULL, 32, "data_ptr");
+  tdesc_create_reg (feature, "esi", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "edi", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "eip", regnum++, 1, NULL, 32, "code_ptr");
+  tdesc_create_reg (feature, "eflags", regnum++, 1, NULL, 32, "i386_eflags");
+  tdesc_create_reg (feature, "cs", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "ss", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "ds", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "es", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "fs", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "gs", regnum++, 1, NULL, 32, "int32");
+  tdesc_create_reg (feature, "st0", regnum++, 1, NULL, 80, "i387_ext");
+  tdesc_create_reg (feature, "st1", regnum++, 1, NULL, 80, "i387_ext");
+  tdesc_create_reg (feature, "st2", regnum++, 1, NULL, 80, "i387_ext");
+  tdesc_create_reg (feature, "st3", regnum++, 1, NULL, 80, "i387_ext");
+  tdesc_create_reg (feature, "st4", regnum++, 1, NULL, 80, "i387_ext");
+  tdesc_create_reg (feature, "st5", regnum++, 1, NULL, 80, "i387_ext");
+  tdesc_create_reg (feature, "st6", regnum++, 1, NULL, 80, "i387_ext");
+  tdesc_create_reg (feature, "st7", regnum++, 1, NULL, 80, "i387_ext");
+  tdesc_create_reg (feature, "fctrl", regnum++, 1, "float", 32, "int");
+  tdesc_create_reg (feature, "fstat", regnum++, 1, "float", 32, "int");
+  tdesc_create_reg (feature, "ftag", regnum++, 1, "float", 32, "int");
+  tdesc_create_reg (feature, "fiseg", regnum++, 1, "float", 32, "int");
+  tdesc_create_reg (feature, "fioff", regnum++, 1, "float", 32, "int");
+  tdesc_create_reg (feature, "foseg", regnum++, 1, "float", 32, "int");
+  tdesc_create_reg (feature, "fooff", regnum++, 1, "float", 32, "int");
+  tdesc_create_reg (feature, "fop", regnum++, 1, "float", 32, "int");
+  return regnum;
+}
diff --git a/gdb/features/i386/32bit-linux.c b/gdb/features/i386/32bit-linux.c
new file mode 100644
index 0000000..3f7bfe7
--- /dev/null
+++ b/gdb/features/i386/32bit-linux.c
@@ -0,0 +1,16 @@
+/* THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi:set ro:
+  Original: 32bit-linux.xml.tmp */
+
+#include "defs.h"
+#include "osabi.h"
+#include "target-descriptions.h"
+
+static int
+create_feature_i386_32bit_linux (struct target_desc *result, long regnum)
+{
+  struct tdesc_feature *feature;
+
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.linux");
+  tdesc_create_reg (feature, "orig_eax", regnum++, 1, NULL, 32, "int");
+  return regnum;
+}
diff --git a/gdb/features/i386/32bit-mpx.c b/gdb/features/i386/32bit-mpx.c
new file mode 100644
index 0000000..50b627e
--- /dev/null
+++ b/gdb/features/i386/32bit-mpx.c
@@ -0,0 +1,53 @@
+/* THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi:set ro:
+  Original: 32bit-mpx.xml.tmp */
+
+#include "defs.h"
+#include "osabi.h"
+#include "target-descriptions.h"
+
+static int
+create_feature_i386_32bit_mpx (struct target_desc *result, long regnum)
+{
+  struct tdesc_feature *feature;
+
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.mpx");
+  struct tdesc_type *field_type;
+  struct tdesc_type *type;
+  type = tdesc_create_struct (feature, "br128");
+  field_type = tdesc_named_type (feature, "uint64");
+  tdesc_add_field (type, "lbound", field_type);
+  field_type = tdesc_named_type (feature, "uint64");
+  tdesc_add_field (type, "ubound_raw", field_type);
+
+  type = tdesc_create_struct (feature, "_bndstatus");
+  tdesc_set_struct_size (type, 8);
+  tdesc_add_bitfield (type, "bde", 2, 31);
+  tdesc_add_bitfield (type, "error", 0, 1);
+
+  type = tdesc_create_union (feature, "status");
+  field_type = tdesc_named_type (feature, "data_ptr");
+  tdesc_add_field (type, "raw", field_type);
+  field_type = tdesc_named_type (feature, "_bndstatus");
+  tdesc_add_field (type, "status", field_type);
+
+  type = tdesc_create_struct (feature, "_bndcfgu");
+  tdesc_set_struct_size (type, 8);
+  tdesc_add_bitfield (type, "base", 12, 31);
+  tdesc_add_bitfield (type, "reserved", 2, 11);
+  tdesc_add_bitfield (type, "preserved", 1, 1);
+  tdesc_add_bitfield (type, "enabled", 0, 0);
+
+  type = tdesc_create_union (feature, "cfgu");
+  field_type = tdesc_named_type (feature, "data_ptr");
+  tdesc_add_field (type, "raw", field_type);
+  field_type = tdesc_named_type (feature, "_bndcfgu");
+  tdesc_add_field (type, "config", field_type);
+
+  tdesc_create_reg (feature, "bnd0raw", regnum++, 1, NULL, 128, "br128");
+  tdesc_create_reg (feature, "bnd1raw", regnum++, 1, NULL, 128, "br128");
+  tdesc_create_reg (feature, "bnd2raw", regnum++, 1, NULL, 128, "br128");
+  tdesc_create_reg (feature, "bnd3raw", regnum++, 1, NULL, 128, "br128");
+  tdesc_create_reg (feature, "bndcfgu", regnum++, 1, NULL, 64, "cfgu");
+  tdesc_create_reg (feature, "bndstatus", regnum++, 1, NULL, 64, "status");
+  return regnum;
+}
diff --git a/gdb/features/i386/32bit-pkeys.c b/gdb/features/i386/32bit-pkeys.c
new file mode 100644
index 0000000..afb4958
--- /dev/null
+++ b/gdb/features/i386/32bit-pkeys.c
@@ -0,0 +1,16 @@
+/* THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi:set ro:
+  Original: 32bit-pkeys.xml.tmp */
+
+#include "defs.h"
+#include "osabi.h"
+#include "target-descriptions.h"
+
+static int
+create_feature_i386_32bit_pkeys (struct target_desc *result, long regnum)
+{
+  struct tdesc_feature *feature;
+
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.pkeys");
+  tdesc_create_reg (feature, "pkru", regnum++, 1, NULL, 32, "uint32");
+  return regnum;
+}
diff --git a/gdb/features/i386/32bit-sse.c b/gdb/features/i386/32bit-sse.c
new file mode 100644
index 0000000..9aa7d3e
--- /dev/null
+++ b/gdb/features/i386/32bit-sse.c
@@ -0,0 +1,76 @@
+/* THIS FILE IS GENERATED.  -*- buffer-read-only: t -*- vi:set ro:
+  Original: 32bit-sse.xml.tmp */
+
+#include "defs.h"
+#include "osabi.h"
+#include "target-descriptions.h"
+
+static int
+create_feature_i386_32bit_sse (struct target_desc *result, long regnum)
+{
+  struct tdesc_feature *feature;
+
+  feature = tdesc_create_feature (result, "org.gnu.gdb.i386.sse");
+  struct tdesc_type *field_type;
+  field_type = tdesc_named_type (feature, "ieee_single");
+  tdesc_create_vector (feature, "v4f", field_type, 4);
+
+  field_type = tdesc_named_type (feature, "ieee_double");
+  tdesc_create_vector (feature, "v2d", field_type, 2);
+
+  field_type = tdesc_named_type (feature, "int8");
+  tdesc_create_vector (feature, "v16i8", field_type, 16);
+
+  field_type = tdesc_named_type (feature, "int16");
+  tdesc_create_vector (feature, "v8i16", field_type, 8);
+
+  field_type = tdesc_named_type (feature, "int32");
+  tdesc_create_vector (feature, "v4i32", field_type, 4);
+
+  field_type = tdesc_named_type (feature, "int64");
+  tdesc_create_vector (feature, "v2i64", field_type, 2);
+
+  struct tdesc_type *type;
+  type = tdesc_create_union (feature, "vec128");
+  field_type = tdesc_named_type (feature, "v4f");
+  tdesc_add_field (type, "v4_float", field_type);
+  field_type = tdesc_named_type (feature, "v2d");
+  tdesc_add_field (type, "v2_double", field_type);
+  field_type = tdesc_named_type (feature, "v16i8");
+  tdesc_add_field (type, "v16_int8", field_type);
+  field_type = tdesc_named_type (feature, "v8i16");
+  tdesc_add_field (type, "v8_int16", field_type);
+  field_type = tdesc_named_type (feature, "v4i32");
+  tdesc_add_field (type, "v4_int32", field_type);
+  field_type = tdesc_named_type (feature, "v2i64");
+  tdesc_add_field (type, "v2_int64", field_type);
+  field_type = tdesc_named_type (feature, "uint128");
+  tdesc_add_field (type, "uint128", field_type);
+
+  type = tdesc_create_flags (feature, "i386_mxcsr", 4);
+  tdesc_add_flag (type, 0, "IE");
+  tdesc_add_flag (type, 1, "DE");
+  tdesc_add_flag (type, 2, "ZE");
+  tdesc_add_flag (type, 3, "OE");
+  tdesc_add_flag (type, 4, "UE");
+  tdesc_add_flag (type, 5, "PE");
+  tdesc_add_flag (type, 6, "DAZ");
+  tdesc_add_flag (type, 7, "IM");
+  tdesc_add_flag (type, 8, "DM");
+  tdesc_add_flag (type, 9, "ZM");
+  tdesc_add_flag (type, 10, "OM");
+  tdesc_add_flag (type, 11, "UM");
+  tdesc_add_flag (type, 12, "PM");
+  tdesc_add_flag (type, 15, "FZ");
+
+  tdesc_create_reg (feature, "xmm0", regnum++, 1, NULL, 128, "vec128");
+  tdesc_create_reg (feature, "xmm1", regnum++, 1, NULL, 128, "vec128");
+  tdesc_create_reg (feature, "xmm2", regnum++, 1, NULL, 128, "vec128");
+  tdesc_create_reg (feature, "xmm3", regnum++, 1, NULL, 128, "vec128");
+  tdesc_create_reg (feature, "xmm4", regnum++, 1, NULL, 128, "vec128");
+  tdesc_create_reg (feature, "xmm5", regnum++, 1, NULL, 128, "vec128");
+  tdesc_create_reg (feature, "xmm6", regnum++, 1, NULL, 128, "vec128");
+  tdesc_create_reg (feature, "xmm7", regnum++, 1, NULL, 128, "vec128");
+  tdesc_create_reg (feature, "mxcsr", regnum++, 1, "vector", 32, "i386_mxcsr");
+  return regnum;
+}
diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index 60bc4e5..10f3be1 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -34,6 +34,7 @@
 #include "gdb_obstack.h"
 #include "hashtab.h"
 #include "inferior.h"
+#include <algorithm>
 
 class tdesc_element_visitor
 {
@@ -42,6 +43,8 @@ public:
   virtual void visit_end (const target_desc *e) = 0;
 
   virtual void visit (const tdesc_feature *e) = 0;
+  virtual void visit_end (const tdesc_feature *e) = 0;
+
   virtual void visit (const tdesc_type *e) = 0;
   virtual void visit (const tdesc_reg *e) = 0;
 };
@@ -306,8 +309,9 @@ typedef struct tdesc_feature : tdesc_element
       {
 	reg->accept (v);
       }
-  }
 
+    v.visit_end (this);
+  }
 } *tdesc_feature_p;
 DEF_VEC_P(tdesc_feature_p);
 
@@ -1872,6 +1876,9 @@ public:
 		       e->name);
   }
 
+  void visit_end (const tdesc_feature *e) override
+  {}
+
   void visit_end (const target_desc *e) override
   {
     printf_unfiltered ("\n  tdesc_%s = result;\n", m_function);
@@ -2030,38 +2037,123 @@ public:
     printf_unfiltered ("%d, \"%s\");\n", reg->bitsize, reg->type);
   }
 
+protected:
+  std::string m_filename_after_features;
+
 private:
   char *m_function;
-  std::string m_filename_after_features;
   bool m_printed_field_type = false;
   bool m_printed_type = false;
 };
 
+class print_c_feature : public print_c_tdesc
+{
+public:
+  print_c_feature (std::string &file)
+    : print_c_tdesc (file)
+  {
+    /* Trim ".tmp".  */
+    auto const pos = m_filename_after_features.find_last_of ('.');
+
+    m_filename_after_features = m_filename_after_features.substr (0, pos);
+  }
+
+  void visit (const target_desc *e) override
+  {
+    printf_unfiltered ("#include \"defs.h\"\n");
+    printf_unfiltered ("#include \"osabi.h\"\n");
+    printf_unfiltered ("#include \"target-descriptions.h\"\n");
+    printf_unfiltered ("\n");
+  }
+
+  void visit_end (const target_desc *e) override
+  {}
+
+  void visit (const tdesc_feature *e) override
+  {
+    std::string name (m_filename_after_features);
+
+    auto pos = name.find_first_of ('.');
+
+    name = name.substr (0, pos);
+    std::replace (name.begin (), name.end (), '/', '_');
+    std::replace (name.begin (), name.end (), '-', '_');
+
+    printf_unfiltered ("static int\n");
+    printf_unfiltered ("create_feature_%s ", name.c_str ());
+    printf_unfiltered ("(struct target_desc *result, long regnum)\n");
+
+    printf_unfiltered ("{\n");
+    printf_unfiltered ("  struct tdesc_feature *feature;\n");
+    printf_unfiltered ("\n  feature = tdesc_create_feature (result, \"%s\");\n",
+		       e->name);
+  }
+
+  void visit_end (const tdesc_feature *e) override
+  {
+    printf_unfiltered ("  return regnum;\n");
+    printf_unfiltered ("}\n");
+  }
+
+  void visit (const tdesc_reg *reg) override
+  {
+    printf_unfiltered ("  tdesc_create_reg (feature, \"%s\", regnum++, %d, ",
+		       reg->name, reg->save_restore);
+    if (reg->group)
+      printf_unfiltered ("\"%s\", ", reg->group);
+    else
+      printf_unfiltered ("NULL, ");
+    printf_unfiltered ("%d, \"%s\");\n", reg->bitsize, reg->type);
+  }
+
+};
+
 static void
 maint_print_c_tdesc_cmd (char *args, int from_tty)
 {
   const struct target_desc *tdesc;
+  const char *filename;
+
+  if (args == NULL)
+    {
+      /* Use the global target-supplied description, not the current
+	 architecture's.  This lets a GDB for one architecture generate C
+	 for another architecture's description, even though the gdbarch
+	 initialization code will reject the new description.  */
+      tdesc = current_target_desc;
+      filename = target_description_filename;
+    }
+  else
+    {
+      /* Use the target description from the XML file.  */
+      filename = args;
+      tdesc = file_read_description_xml (filename);
+    }
 
-  /* Use the global target-supplied description, not the current
-     architecture's.  This lets a GDB for one architecture generate C
-     for another architecture's description, even though the gdbarch
-     initialization code will reject the new description.  */
-  tdesc = current_target_desc;
   if (tdesc == NULL)
     error (_("There is no target description to print."));
 
-  if (target_description_filename == NULL)
+  if (filename == NULL)
     error (_("The current target description did not come from an XML file."));
 
-  std::string filename_after_features (target_description_filename);
+  std::string filename_after_features (filename);
   auto loc = filename_after_features.rfind ("/features/");
 
   if (loc != std::string::npos)
     filename_after_features = filename_after_features.substr (loc + 10);
 
-  print_c_tdesc v (filename_after_features);
+  if (strncmp (filename_after_features.c_str(), "i386/32bit-", 11) == 0)
+    {
+      print_c_feature v (filename_after_features);
+
+      tdesc->accept (v);
+    }
+  else
+    {
+      print_c_tdesc v (filename_after_features);
 
-  tdesc->accept (v);
+      tdesc->accept (v);
+    }
 }
 
 /* Provide a prototype to silence -Wmissing-prototypes.  */