diff --git a/scripts/decodetree.py b/scripts/decodetree.py
index f6f7368774..d8c59cab60 100755
--- a/scripts/decodetree.py
+++ b/scripts/decodetree.py
@@ -33,6 +33,7 @@ arguments = {}
 formats = {}
 patterns = []
 allpatterns = []
+anyextern = False
 
 translate_prefix = 'trans'
 translate_scope = 'static '
@@ -482,12 +483,14 @@ def parse_arguments(lineno, name, toks):
     """Parse one argument set from TOKS at LINENO"""
     global arguments
     global re_ident
+    global anyextern
 
     flds = []
     extern = False
     for t in toks:
         if re_fullmatch('!extern', t):
             extern = True
+            anyextern = True
             continue
         if not re_fullmatch(re_ident, t):
             error(lineno, 'invalid argument set token "{0}"'.format(t))
@@ -1188,6 +1191,7 @@ def main():
     global insnmask
     global decode_function
     global variablewidth
+    global anyextern
 
     decode_scope = 'static '
 
@@ -1248,6 +1252,19 @@ def main():
     # A single translate function can be invoked for different patterns.
     # Make sure that the argument sets are the same, and declare the
     # function only once.
+    #
+    # If we're sharing formats, we're likely also sharing trans_* functions,
+    # but we can't tell which ones.  Prevent issues from the compiler by
+    # suppressing redundant declaration warnings.
+    if anyextern:
+        output("#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE\n",
+               "# pragma GCC diagnostic push\n",
+               "# pragma GCC diagnostic ignored \"-Wredundant-decls\"\n",
+               "# ifdef __clang__\n"
+               "#  pragma GCC diagnostic ignored \"-Wtypedef-redefinition\"\n",
+               "# endif\n",
+               "#endif\n\n")
+
     out_pats = {}
     for i in allpatterns:
         if i.name in out_pats:
@@ -1259,6 +1276,11 @@ def main():
             out_pats[i.name] = i
     output('\n')
 
+    if anyextern:
+        output("#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE\n",
+               "# pragma GCC diagnostic pop\n",
+               "#endif\n\n")
+
     for n in sorted(formats.keys()):
         f = formats[n]
         f.output_extract()