Implement parameter fields.

Push warning pragmas into the generated code.
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Merge remote-tracking branch 'remotes/rth/tags/pull-dt-20190819' into staging

Implement parameter fields.
Push warning pragmas into the generated code.

# gpg: Signature made Mon 19 Aug 2019 16:14:41 BST
# gpg:                using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F
# gpg:                issuer "richard.henderson@linaro.org"
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [full]
# Primary key fingerprint: 7A48 1E78 868B 4DB6 A85A  05C0 64DF 38E8 AF7E 215F

* remotes/rth/tags/pull-dt-20190819:
  target/riscv: Remove redundant declaration pragmas
  decodetree: Suppress redundant declaration warnings
  decodetree: Allow !function with no input bits

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

docs/devel/decodetree.rst

@@ -23,7 +23,7 @@ Fields
 
 Syntax::
 
-  field_def     := '%' identifier ( unnamed_field )+ ( !function=identifier )?
+  field_def     := '%' identifier ( unnamed_field )* ( !function=identifier )?
   unnamed_field := number ':' ( 's' ) number
 
 For *unnamed_field*, the first number is the least-significant bit position
@@ -34,6 +34,12 @@ present, they are concatenated.  In this way one can define disjoint fields.
 If ``!function`` is specified, the concatenated result is passed through the
 named function, taking and returning an integral value.
 
+One may use ``!function`` with zero ``unnamed_fields``.  This case is called
+a *parameter*, and the named function is only passed the ``DisasContext``
+and returns an integral value extracted from there.
+
+A field with no ``unnamed_fields`` and no ``!function`` is in error.
+
 FIXME: the fields of the structure into which this result will be stored
 is restricted to ``int``.  Which means that we cannot expand 64-bit items.
 

scripts/decodetree.py

@@ -33,6 +33,7 @@ arguments = {}
 formats = {}
 patterns = []
 allpatterns = []
+anyextern = False
 
 translate_prefix = 'trans'
 translate_scope = 'static '
@@ -245,7 +246,7 @@ class ConstField:
 
 
 class FunctionField:
-    """Class representing a field passed through an expander"""
+    """Class representing a field passed through a function"""
     def __init__(self, func, base):
         self.mask = base.mask
         self.sign = base.sign
@@ -266,6 +267,27 @@ class FunctionField:
 # end FunctionField
 
 
+class ParameterField:
+    """Class representing a pseudo-field read from a function"""
+    def __init__(self, func):
+        self.mask = 0
+        self.sign = 0
+        self.func = func
+
+    def __str__(self):
+        return self.func
+
+    def str_extract(self):
+        return self.func + '(ctx)'
+
+    def __eq__(self, other):
+        return self.func == other.func
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+# end ParameterField
+
+
 class Arguments:
     """Class representing the extracted fields of a format"""
     def __init__(self, nm, flds, extern):
@@ -433,17 +455,23 @@ def parse_field(lineno, name, toks):
 
     if width > insnwidth:
         error(lineno, 'field too large')
-    if len(subs) == 1:
-        f = subs[0]
+    if len(subs) == 0:
+        if func:
+            f = ParameterField(func)
+        else:
+            error(lineno, 'field with no value')
     else:
-        mask = 0
-        for s in subs:
-            if mask & s.mask:
-                error(lineno, 'field components overlap')
-            mask |= s.mask
-        f = MultiField(subs, mask)
-    if func:
-        f = FunctionField(func, f)
+        if len(subs) == 1:
+            f = subs[0]
+        else:
+            mask = 0
+            for s in subs:
+                if mask & s.mask:
+                    error(lineno, 'field components overlap')
+                mask |= s.mask
+            f = MultiField(subs, mask)
+        if func:
+            f = FunctionField(func, f)
 
     if name in fields:
         error(lineno, 'duplicate field', name)
@@ -455,12 +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))
@@ -1161,6 +1191,7 @@ def main():
     global insnmask
     global decode_function
     global variablewidth
+    global anyextern
 
     decode_scope = 'static '
 
@@ -1221,6 +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:
@@ -1232,6 +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()

target/riscv/translate.c

@@ -708,26 +708,9 @@ static bool gen_shift(DisasContext *ctx, arg_r *a,
 #include "insn_trans/trans_rvd.inc.c"
 #include "insn_trans/trans_privileged.inc.c"
 
-/*
- * Auto-generated decoder.
- * Note that the 16-bit decoder reuses some of the trans_* functions
- * initially declared by the 32-bit decoder, which results in duplicate
- * declaration warnings.  Suppress them.
- */
-#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
-# pragma GCC diagnostic push
-# pragma GCC diagnostic ignored "-Wredundant-decls"
-# ifdef __clang__
-#  pragma GCC diagnostic ignored "-Wtypedef-redefinition"
-# endif
-#endif
-
+/* Include the auto-generated decoder for 16 bit insn */
 #include "decode_insn16.inc.c"
 
-#ifdef CONFIG_PRAGMA_DIAGNOSTIC_AVAILABLE
-# pragma GCC diagnostic pop
-#endif
-
 static void decode_opc(DisasContext *ctx)
 {
     /* check for compressed insn */

tests/decode/err_field6.decode

@@ -0,0 +1,5 @@
+# This work is licensed under the terms of the GNU LGPL, version 2 or later.
+# See the COPYING.LIB file in the top-level directory.
+
+# Diagnose no bits in field
+%field

tests/decode/succ_function.decode

@@ -0,0 +1,6 @@
+# This work is licensed under the terms of the GNU LGPL, version 2 or later.
+# See the COPYING.LIB file in the top-level directory.
+
+# "Field" as parameter pulled from DisasContext.
+%foo  !function=foo
+foo   00000000000000000000000000000000 %foo