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".

1 files changed, 103 insertions, 11 deletions

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.  */