[3.4/3.5 PATCH] Fix target/16649 ICE on x86-darwin

[Andrew Pinski]

GCC rejects some constant RTL which are valid for x86-darwin:
(const:SI (minus:SI (symbol_ref:SI ("&L___keymgr_global$non_lazy_ptr"))
                     (symbol_ref:SI ("<pic base>")))

This is a fall out of the patch to fix PR target/15717.

This patch fixes it by accepting the above RTL as it is a valid constant
on x86-darwin.
OK for the mainline and the 3.4 branch?  Tested with a cross compiler 
from
powerpc-apple-darwin to i686-pc-darwin and ran into another bug, PR 
16651
when building libstdc++.


Thanks,
Andrew Pinski


ChangeLog:
	* config/i386/i386.c (legitimate_constant_p): For Darwin,
	accept {LABEL | SYMBOL}_REF - SYMBOL_REF-FOR-PICBASE as a constant
	expression.

Index: i386.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/config/i386/i386.c,v
retrieving revision 1.696
diff -u -p -r1.696 i386.c
--- i386.c	20 Jul 2004 12:25:51 -0000	1.696
+++ i386.c	21 Jul 2004 00:23:58 -0000
@@ -5896,6 +5896,19 @@ legitimate_constant_p (rtx x)
        if (GET_CODE (inner) == PLUS
  	  && tls_symbolic_operand (XEXP (inner, 0), Pmode))
  	return false;
+	
+	/* Allow {LABEL | SYMBOL}_REF - SYMBOL_REF-FOR-PICBASE for Mach-O.  */
+	if (TARGET_MACHO && GET_CODE (inner) == MINUS)
+	  {
+	    if (GET_CODE (XEXP (inner, 0)) == LABEL_REF
+		|| GET_CODE (XEXP (inner, 0)) == SYMBOL_REF)
+	      if (GET_CODE (XEXP (inner, 1)) == SYMBOL_REF)
+		{
+		  const char *sym_name = XSTR (XEXP (inner, 1), 0);
+		  if (! strcmp (sym_name, "<pic base>"))
+		    return 1;
+		}
+	  }

        if (GET_CODE (inner) == PLUS
  	  || GET_CODE (inner) == MINUS)