gas: fix bogus error on .org involving expression

For years I have been carrying this change, and it was long forgotten
what it was originally meant to deal with, hence I've never submitted
it. Until I came across an issue with Linux kernel like alternative
instruction patching, where the space needed to hold the replacement
instruction was allocated using .org. Things built fine for me (since
I had the patch in place), and things also built fine on 2.20. But
assemblers from at least 2.22 onwards produce an undefined symbol
warning for the "orig" label in the new test case, followed by an
error complaining that .org would be moving backwards (which is a
logical consequence of the undefined symbol getting replaced by plain
zero).

gas/
2016-03-22  Jan Beulich  <jbeulich@suse.com>

	* config/tc-hppa.c (get_expression): Also allow expr_section.
	* config/tc-i386.c (i386_finalize_immediate): Likewise.
	(i386_finalize_displacement): Likewise.
	* expr.c (expr): Set retval to expr_section for expressions
	involving symbols, which cannot be resolved right away.

gas/testsuite/
2016-03-22  Jan Beulich  <jbeulich@suse.com>

	* expr-org.s, expr.org.d: New.
	* gas.exp: Run new test.

--- 2016-03-22/gas/config/tc-hppa.c
+++ 2016-03-22/gas/config/tc-hppa.c
@@ -1282,6 +1282,7 @@ get_expression (char *str)
   input_line_pointer = str;
   seg = expression (&the_insn.exp);
   if (!(seg == absolute_section
+	|| seg == expr_section
 	|| seg == undefined_section
 	|| SEG_NORMAL (seg)))
     {
--- 2016-03-22/gas/config/tc-i386.c
+++ 2016-03-22/gas/config/tc-i386.c
@@ -8043,6 +8043,7 @@ i386_finalize_immediate (segT exp_seg AT
 	   && exp_seg != text_section
 	   && exp_seg != data_section
 	   && exp_seg != bss_section
+	   && exp_seg != expr_section
 	   && exp_seg != undefined_section
 	   && !bfd_is_com_section (exp_seg))
     {
@@ -8336,6 +8337,7 @@ i386_finalize_displacement (segT exp_seg
 	   && exp_seg != text_section
 	   && exp_seg != data_section
 	   && exp_seg != bss_section
+	   && exp_seg != expr_section
 	   && exp_seg != undefined_section
 	   && !bfd_is_com_section (exp_seg))
     {
--- 2016-03-22/gas/expr.c
+++ 2016-03-22/gas/expr.c
@@ -1998,7 +1998,11 @@ expr (int rankarg,		/* Larger # is highe
 		  retval = absolute_section;
 		  rightseg = absolute_section;
 		}
+	      else
+		retval = expr_section;
 	    }
+	  else
+	    retval = expr_section;
 	}
       else
 	{
@@ -2010,17 +2014,18 @@ expr (int rankarg,		/* Larger # is highe
 	  resultP->X_add_number = 0;
 	  resultP->X_unsigned = 1;
 	  resultP->X_extrabit = 0;
+	  retval = expr_section;
 	}
 
       if (retval != rightseg)
 	{
-	  if (retval == undefined_section)
+	  if (retval == expr_section)
 	    ;
-	  else if (rightseg == undefined_section)
+	  else if (rightseg == expr_section)
 	    retval = rightseg;
-	  else if (retval == expr_section)
+	  else if (retval == undefined_section)
 	    ;
-	  else if (rightseg == expr_section)
+	  else if (rightseg == undefined_section)
 	    retval = rightseg;
 	  else if (retval == reg_section)
 	    ;
--- 2016-03-22/gas/testsuite/gas/all/expr-org.d
+++ 2016-03-22/gas/testsuite/gas/all/expr-org.d
@@ -0,0 +1,11 @@
+#objdump: -s -j .data -j .alt
+#name: .org with expression (with forward reference)
+
+.*: .*
+
+Contents of section \.data:
+ 0000 [0f][0f]ffff[0f][0f] 01[0 .]*
+
+Contents of section \.alt:
+ 0000 00000000 [ .]*
+#pass
--- 2016-03-22/gas/testsuite/gas/all/expr-org.s
+++ 2016-03-22/gas/testsuite/gas/all/expr-org.s
@@ -0,0 +1,10 @@
+	.data
+orig:
+	.byte	0
+	.org	orig + (alt_end - alt_begin), 0xff
+	.pushsection .alt, "a", %progbits
+alt_begin:
+	.long	0
+alt_end:
+	.popsection
+	.byte	1
--- 2016-03-22/gas/testsuite/gas/all/gas.exp
+++ 2016-03-22/gas/testsuite/gas/all/gas.exp
@@ -432,6 +432,11 @@ gas_test_error "weakref4.s" "" "is alrea
 run_dump_test string
 if [is_elf_format] {
     run_dump_test none
+
+# Targets enabling OBJ_COMPLEX_RELC don't seem to be compatible with this.
+    if { ![istarget "mep-*-*"] } {
+	run_dump_test expr-org
+    }
 }
 
 run_dump_test quoted-sym-names