mem-ruby: allow qualifiers in SLICC functions

All parameters in functions defined within SLICC are const& by default
(except for the implicit types, e.g. TBE). This allow us to specify
if we want to pass parameters as & or const&. Default behavior is
maintained.

A use case is to allow refactoring of common code in actions that
enqueue messages. Messages can be passed as a non-const ref. to
to functions with common initialization. E.g.:

void initRequestMsg(RequestMsg & out_msg) {
  // Common msg init code
}

action(sendRequest1, ...) {
  enqueue(...) {
    initRequestMsg(out_msg);
    // Request1 specific code
  }
}

action(sendRequest2, ...) {
  enqueue(...) {
    initRequestMsg(out_msg);
    // Request2 specific code
  }
}

Change-Id: Ic6a18169a661b3e36710b2a9f8a0e6bc5fce40f8
Signed-off-by: Tiago Mück <tiago.muck@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/31259
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/mem/slicc/ast/FormalParamAST.py

@@ -1,3 +1,15 @@
+# Copyright (c) 2020 ARM Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
 # Copyright (c) 1999-2008 Mark D. Hill and David A. Wood
 # Copyright (c) 2009 The Hewlett-Packard Development Company
 # All rights reserved.
@@ -29,12 +41,12 @@ from slicc.ast.AST import AST
 from slicc.symbols import Var
 
 class FormalParamAST(AST):
-    def __init__(self, slicc, type_ast, ident, default = None, pointer = False):
+    def __init__(self, slicc, type_ast, ident, default = None, qualifier=""):
         super(FormalParamAST, self).__init__(slicc)
         self.type_ast = type_ast
         self.ident = ident
         self.default = default
-        self.pointer = pointer
+        self.qualifier = qualifier
 
     def __repr__(self):
         return "[FormalParamAST: %s]" % self.ident
@@ -52,11 +64,26 @@ class FormalParamAST(AST):
                 self.pairs)
         self.symtab.newSymbol(v)
 
-        if self.pointer or str(type) == "TBE" or (
-        # Check whether type is entry by checking the interface since
-        # in protocol files, entries use AbstractCacheEntry as interfaces.
+        # Qualifier is always a pointer for TBE table and Cache entries.
+        # It's expected to be left unspecified or specified as ptr.
+        qualifier = self.qualifier
+        if str(type) == "TBE" or (
            "interface" in type and (
                type["interface"] == "AbstractCacheEntry")):
+            if qualifier not in ["", "PTR"] :
+                self.warning("Parameter \'%s\' is always pointer. "
+                             "%s qualifier ignored" % (self.ident, qualifier))
+            qualifier = "PTR"
+
+        # default
+        if qualifier == "":
+            qualifier = "CONST_REF"
+
+        if qualifier == "PTR":
             return type, "%s* %s" % (type.c_ident, param)
-        else:
+        elif qualifier == "REF":
+            return type, "%s& %s" % (type.c_ident, param)
+        elif qualifier == "CONST_REF":
             return type, "const %s& %s" % (type.c_ident, param)
+        else:
+            self.error("Invalid qualifier for param \'%s\'" % self.ident)

src/mem/slicc/parser.py

@@ -1,3 +1,15 @@
+# Copyright (c) 2020 ARM Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
 # Copyright (c) 2009 The Hewlett-Packard Development Company
 # Copyright (c) 2017 Google Inc.
 # All rights reserved.
@@ -132,7 +144,8 @@ class SLICC(Grammar):
                'INCR', 'DECR',
                'DOUBLE_COLON', 'SEMI',
                'ASSIGN', 'DOT',
-               'IDENT', 'LIT_BOOL', 'FLOATNUMBER', 'NUMBER', 'STRING' ]
+               'IDENT', 'LIT_BOOL', 'FLOATNUMBER', 'NUMBER', 'STRING',
+               'AMP', 'CONST' ]
     tokens += reserved.values()
 
     t_EQ = r'=='
@@ -149,6 +162,8 @@ class SLICC(Grammar):
     t_PLUS = r'\+'
     t_DASH = r'-'
     t_STAR = r'\*'
+    t_AMP = r'&'
+    t_CONST = r'const'
     t_SLASH = r'/'
     t_MOD = r'%'
     t_DOUBLE_COLON = r'::'
@@ -433,11 +448,19 @@ class SLICC(Grammar):
 
     def p_param__pointer(self, p):
         "param : type STAR ident"
-        p[0] = ast.FormalParamAST(self, p[1], p[3], None, True)
+        p[0] = ast.FormalParamAST(self, p[1], p[3], None, "PTR")
+
+    def p_param__ref(self, p):
+        "param : type AMP ident"
+        p[0] = ast.FormalParamAST(self, p[1], p[3], None, "REF")
+
+    def p_param__const_ref(self, p):
+        "param : CONST type AMP ident"
+        p[0] = ast.FormalParamAST(self, p[1], p[3], None, "CONST_REF")
 
     def p_param__pointer_default(self, p):
         "param : type STAR ident ASSIGN STRING"
-        p[0] = ast.FormalParamAST(self, p[1], p[3], p[5], True)
+        p[0] = ast.FormalParamAST(self, p[1], p[3], p[5], "PTR")
 
     def p_param__default_number(self, p):
         "param : type ident ASSIGN NUMBER"