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To: gcc-patches@gcc.gnu.org
From: Paolo Bonzini <bonzini@gnu.org>
Subject: Re: RFC: define_predicate
Date: Mon, 02 Aug 2004 14:33:00 -0000
Message-ID: <410E4EF3.603@gnu.org>
References: <87u0vx99j5.fsf@codesourcery.com>
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> (define_predicate "call_operand" "subreg,reg,symbol_ref"
> {
>   if (mode != GET_MODE (op) && mode != VOIDmode)
>     return 0;
> 
>   return (GET_CODE (op) == SYMBOL_REF || GET_CODE (op) == REG
>           || (GET_CODE (op) == SUBREG && GET_CODE (XEXP (op, 0)) == REG));
> })

This could be simplified more, as in

if (GET_CODE (op) == SUBREG)
   return REG_P (XEXP (op, 0)) && call_operand (XEXP (op, 0), mode);
else
   return (mode == GET_MODE (op) || mode == VOIDmode);

if genpreds.c would put an additional switch statement before the user 
code.  Well, maybe in this case it is not that much more readable (maybe 
the opposite is true), but in many predicates the third argument to 
define_predicate would be superfluous, as in

+;; Return 1 if OP refers to a symbol.
+(define_predicate "symbolic_operand" "symbol_ref,const,label_ref"
+{
+  switch (GET_CODE (op))
+    {
+    case CONST:
+    case SYMBOL_REF:
+    case LABEL_REF:
+      return 1;
+
+    default:
+      break;
+    }
+  return 0;
+})

and that argument could be made optional (defaulting to "return 1;"). 
Does this make sense?

Paolo