genattrtab: Parenthesize expressions correctly (PR92107)

As PR92107 shows, genattrtab doesn't parenthesize expressions correctly
(or at all, even).  This fixes it.


	PR rtl-optimization/92107
	* genattrtab.c (write_attr_value) <do_operator>: Parenthesize the
	expression written.

From-SVN: r277023

gcc/ChangeLog

+2019-10-15  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/92107
+	* genattrtab.c (write_attr_value) <do_operator>: Parenthesize the
+	expression written.
+
 2019-10-15  Iain Sandoe  <iain@sandoe.co.uk>
 
 	* config/darwin.c: Update description of fix and continue.

gcc/genattrtab.c

@@ -4425,11 +4425,11 @@ write_attr_value (FILE *outf, class attr_desc *attr, rtx value)
       goto do_operator;
 
     do_operator:
+      fprintf (outf, "(");
       write_attr_value (outf, attr, XEXP (value, 0));
-      fputc (' ', outf);
-      fputc (op,  outf);
-      fputc (' ', outf);
+      fprintf (outf, " %c ", op);
       write_attr_value (outf, attr, XEXP (value, 1));
+      fprintf (outf, ")");
       break;
 
     case IF_THEN_ELSE: