From: Akihiko Odaki <akihiko.odaki@daynix.com>

Currently the number of registers exposed to GDB is written as magic
numbers in code. Derive the number of registers GDB actually see from
XML files to replace the magic numbers in code later.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20231025093128.33116-2-akihiko.odaki@daynix.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
---
 include/exec/gdbstub.h  |  1 +
 scripts/feature_to_c.py | 46 +++++++++++++++++++++++++++++++++++++++--
 2 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/include/exec/gdbstub.h b/include/exec/gdbstub.h
index 1a01c35f8e..a43aa34dad 100644
--- a/include/exec/gdbstub.h
+++ b/include/exec/gdbstub.h
@@ -13,6 +13,7 @@
 typedef struct GDBFeature {
     const char *xmlname;
     const char *xml;
+    int num_regs;
 } GDBFeature;
 
 
diff --git a/scripts/feature_to_c.py b/scripts/feature_to_c.py
index bcbcb83beb..e04d6b2df7 100644
--- a/scripts/feature_to_c.py
+++ b/scripts/feature_to_c.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0-or-later
 
-import os, sys
+import os, sys, xml.etree.ElementTree
 
 def writeliteral(indent, bytes):
     sys.stdout.write(' ' * indent)
@@ -39,10 +39,52 @@ def writeliteral(indent, bytes):
     with open(input, 'rb') as file:
         read = file.read()
 
+    parser = xml.etree.ElementTree.XMLPullParser(['start', 'end'])
+    parser.feed(read)
+    events = parser.read_events()
+    event, element = next(events)
+    if event != 'start':
+        sys.stderr.write(f'unexpected event: {event}\n')
+        exit(1)
+    if element.tag != 'feature':
+        sys.stderr.write(f'unexpected start tag: {element.tag}\n')
+        exit(1)
+
+    regnum = 0
+    regnums = []
+    tags = ['feature']
+    for event, element in events:
+        if event == 'end':
+            if element.tag != tags[len(tags) - 1]:
+                sys.stderr.write(f'unexpected end tag: {element.tag}\n')
+                exit(1)
+
+            tags.pop()
+            if element.tag == 'feature':
+                break
+        elif event == 'start':
+            if len(tags) < 2 and element.tag == 'reg':
+                if 'regnum' in element.attrib:
+                    regnum = int(element.attrib['regnum'])
+
+                regnums.append(regnum)
+                regnum += 1
+
+            tags.append(element.tag)
+        else:
+            raise Exception(f'unexpected event: {event}\n')
+
+    if len(tags):
+        sys.stderr.write('unterminated feature tag\n')
+        exit(1)
+
+    base_reg = min(regnums)
+    num_regs = max(regnums) - base_reg + 1 if len(regnums) else 0
+
     sys.stdout.write('    {\n')
     writeliteral(8, bytes(os.path.basename(input), 'utf-8'))
     sys.stdout.write(',\n')
     writeliteral(8, read)
-    sys.stdout.write('\n    },\n')
+    sys.stdout.write(f',\n        {num_regs},\n    }},\n')
 
 sys.stdout.write('    { NULL }\n};\n')
-- 
2.39.2