[PATCH/RFA] Do not emit "field_type" var if not needed on "maint print c-tdesc"

[Sergio Durigan Junior <sergiodj at redhat dot com>]

While fiddling a bit with -Wunused-variable, I noticed that "maint
print c-tdesc" was always generating code for the
"tdesc_type *field_type" variable, even when it wasn't used.  This is
caught by GCC when using -Wunused-variable, of course.  So I modified
the "print_c_tdesc" class to check whether "field_type" will be needed
or not.

In order to do the check, I basically copied the logic implemented on
"void visit (const tdesc_type_with_fields *type)", specifically the
"switch" part, and simplified it to determine which types need
"field_type".  It's on a new simple function called
"need_field_type".  Then, we can simply call this function when
deciding whether to print "field_type", and that's it.

I've also regenerated all the C files under gdb/features/, and as
expected only those that don't need "field_type" were modified.

yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* features/aarch64-core.c: Regenerate.
	* features/arc-arcompact.c: Regenerate.
	* features/arc-v2.c: Regenerate.
	* features/i386/32bit-core.c: Regenerate.
	* features/i386/64bit-core.c: Regenerate.
	* features/i386/x32-core.c: Regenerate.
	* features/or1k.c: Regenerate.
	* target-descriptions.c (class print_c_tdesc)
	<need_field_type>: New method.
---
 gdb/features/aarch64-core.c    |  1 -
 gdb/features/arc-arcompact.c   |  1 -
 gdb/features/arc-v2.c          |  1 -
 gdb/features/i386/32bit-core.c |  1 -
 gdb/features/i386/64bit-core.c |  1 -
 gdb/features/i386/x32-core.c   |  1 -
 gdb/features/or1k.c            |  1 -
 gdb/target-descriptions.c      | 41 ++++++++++++++++++++++++++++++++++++++++-
 8 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/gdb/features/aarch64-core.c b/gdb/features/aarch64-core.c
index 618a7ef787..3707b7e055 100644
--- a/gdb/features/aarch64-core.c
+++ b/gdb/features/aarch64-core.c
@@ -10,7 +10,6 @@ create_feature_aarch64_core (struct target_desc *result, long regnum)
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.aarch64.core", "aarch64-core.xml");
   tdesc_type_with_fields *type_with_fields;
-  tdesc_type *field_type;
   type_with_fields = tdesc_create_flags (feature, "cpsr_flags", 4);
   tdesc_add_flag (type_with_fields, 0, "SP");
   tdesc_add_flag (type_with_fields, 1, "");
diff --git a/gdb/features/arc-arcompact.c b/gdb/features/arc-arcompact.c
index 79b6889172..f81f0a26ba 100644
--- a/gdb/features/arc-arcompact.c
+++ b/gdb/features/arc-arcompact.c
@@ -52,7 +52,6 @@ initialize_tdesc_arc_arcompact (void)
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.arc.aux-minimal");
   tdesc_type_with_fields *type_with_fields;
-  tdesc_type *field_type;
   type_with_fields = tdesc_create_flags (feature, "status32_type", 4);
   tdesc_add_flag (type_with_fields, 0, "H");
   tdesc_add_bitfield (type_with_fields, "E", 1, 2);
diff --git a/gdb/features/arc-v2.c b/gdb/features/arc-v2.c
index 9908b4c5ec..b2254b293c 100644
--- a/gdb/features/arc-v2.c
+++ b/gdb/features/arc-v2.c
@@ -52,7 +52,6 @@ initialize_tdesc_arc_v2 (void)
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.arc.aux-minimal");
   tdesc_type_with_fields *type_with_fields;
-  tdesc_type *field_type;
   type_with_fields = tdesc_create_flags (feature, "status32_type", 4);
   tdesc_add_flag (type_with_fields, 0, "H");
   tdesc_add_bitfield (type_with_fields, "E", 1, 4);
diff --git a/gdb/features/i386/32bit-core.c b/gdb/features/i386/32bit-core.c
index de2ce474d5..294e86d81e 100644
--- a/gdb/features/i386/32bit-core.c
+++ b/gdb/features/i386/32bit-core.c
@@ -10,7 +10,6 @@ create_feature_i386_32bit_core (struct target_desc *result, long regnum)
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core", "32bit-core.xml");
   tdesc_type_with_fields *type_with_fields;
-  tdesc_type *field_type;
   type_with_fields = tdesc_create_flags (feature, "i386_eflags", 4);
   tdesc_add_flag (type_with_fields, 0, "CF");
   tdesc_add_flag (type_with_fields, 1, "");
diff --git a/gdb/features/i386/64bit-core.c b/gdb/features/i386/64bit-core.c
index f4cad06e66..9e39ee42d9 100644
--- a/gdb/features/i386/64bit-core.c
+++ b/gdb/features/i386/64bit-core.c
@@ -10,7 +10,6 @@ create_feature_i386_64bit_core (struct target_desc *result, long regnum)
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core", "64bit-core.xml");
   tdesc_type_with_fields *type_with_fields;
-  tdesc_type *field_type;
   type_with_fields = tdesc_create_flags (feature, "i386_eflags", 4);
   tdesc_add_flag (type_with_fields, 0, "CF");
   tdesc_add_flag (type_with_fields, 1, "");
diff --git a/gdb/features/i386/x32-core.c b/gdb/features/i386/x32-core.c
index acafc7dace..c268e11bea 100644
--- a/gdb/features/i386/x32-core.c
+++ b/gdb/features/i386/x32-core.c
@@ -10,7 +10,6 @@ create_feature_i386_x32_core (struct target_desc *result, long regnum)
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.i386.core", "x32-core.xml");
   tdesc_type_with_fields *type_with_fields;
-  tdesc_type *field_type;
   type_with_fields = tdesc_create_flags (feature, "i386_eflags", 4);
   tdesc_add_flag (type_with_fields, 0, "CF");
   tdesc_add_flag (type_with_fields, 1, "");
diff --git a/gdb/features/or1k.c b/gdb/features/or1k.c
index 929a5f9208..9169cae940 100644
--- a/gdb/features/or1k.c
+++ b/gdb/features/or1k.c
@@ -16,7 +16,6 @@ initialize_tdesc_or1k (void)
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.or1k.group0");
   tdesc_type_with_fields *type_with_fields;
-  tdesc_type *field_type;
   type_with_fields = tdesc_create_flags (feature, "sr_flags", 4);
   tdesc_add_flag (type_with_fields, 0, "SM");
   tdesc_add_flag (type_with_fields, 1, "TEE");
diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index 88ac55f404..fe4b5efbf5 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -1886,6 +1886,44 @@ public:
     printf_unfiltered ("\n");
   }
 
+  /* Some targets don't need the "tdesc_type *field_type" variable.
+     This function returns true if TYPE is going to need it, false
+     otherwise.  */
+  bool need_field_type (const tdesc_type_with_fields *type)
+  {
+    switch (type->kind)
+      {
+      case TDESC_TYPE_UNION:
+	return true;
+
+      case TDESC_TYPE_ENUM:
+	return false;
+
+      case TDESC_TYPE_STRUCT:
+      case TDESC_TYPE_FLAGS:
+	for (const tdesc_type_field &f : type->fields)
+	  {
+	    if (f.start != -1)
+	      {
+		if (f.type->kind == TDESC_TYPE_BOOL)
+		  continue;
+		else if ((type->size == 4 && f.type->kind == TDESC_TYPE_UINT32)
+			 || (type->size == 8
+			     && f.type->kind == TDESC_TYPE_UINT64))
+		  continue;
+		else
+		  return true;
+	      }
+	    else /* Not a bitfield.  */
+	      return true;
+	  }
+	break;
+      default:
+	error (_("C output is not supported type \"%s\"."), type->name.c_str ());
+      }
+    return false;
+  }
+
   void visit (const tdesc_type_with_fields *type) override
   {
     if (!m_printed_type_with_fields)
@@ -1895,7 +1933,8 @@ public:
       }
 
     if (!type->fields.empty ()
-	&& !m_printed_field_type)
+	&& !m_printed_field_type
+	&& need_field_type (type))
       {
 	printf_unfiltered ("  tdesc_type *field_type;\n");
 	m_printed_field_type = true;
-- 
2.14.3