* config/tc-avr.c: Add specified_mcu variable for selected mcu.

(enum options): add OPTION_RMW_ISA for -mrmw option.
	(struct option md_longopts): Add mrmw option.
	(md_show_usage): add -mrmw option description.
	(md_parse_option): Update isa details if -mrmw option specified.
	* doc/c-avr.texi: Add doc for new option -mrmw.
	* gas/avr/avr.exp: Run new tests.
	* gas/avr/rmw.d: Add test for additional ISA support.
	* gas/avr/rmw.s: Ditto.

gas/config/tc-avr.c

@@ -326,8 +326,10 @@ static struct mcu_type_s mcu_types[] =
   {NULL, 0, 0}
 };
 
+
 /* Current MCU type.  */
 static struct mcu_type_s   default_mcu = {"avr2", AVR_ISA_AVR2, bfd_mach_avr2};
+static struct mcu_type_s   specified_mcu;
 static struct mcu_type_s * avr_mcu = & default_mcu;
 
 /* AVR target-specific switches.  */
@@ -398,7 +400,8 @@ enum options
 {
   OPTION_ALL_OPCODES = OPTION_MD_BASE + 1,
   OPTION_NO_SKIP_BUG,
-  OPTION_NO_WRAP
+  OPTION_NO_WRAP,
+  OPTION_ISA_RMW
 };
 
 struct option md_longopts[] =
@@ -407,6 +410,7 @@ struct option md_longopts[] =
   { "mall-opcodes", no_argument, NULL, OPTION_ALL_OPCODES },
   { "mno-skip-bug", no_argument, NULL, OPTION_NO_SKIP_BUG },
   { "mno-wrap",     no_argument, NULL, OPTION_NO_WRAP     },
+  { "mrmw",         no_argument, NULL, OPTION_ISA_RMW     },
   { NULL, no_argument, NULL, 0 }
 };
 
@@ -511,7 +515,9 @@ md_show_usage (FILE *stream)
 	"  -mno-skip-bug    disable warnings for skipping two-word instructions\n"
 	"                   (default for avr4, avr5)\n"
 	"  -mno-wrap        reject rjmp/rcall instructions with 8K wrap-around\n"
-	"                   (default for avr3, avr5)\n"));
+	"                   (default for avr3, avr5)\n"
+	"  -mrmw            accept Read-Modify-Write instructions\n"
+    ));
   show_mcu_list (stream);
 }
 
@@ -558,7 +564,12 @@ md_parse_option (int c, char *arg)
 	   type - this for allows passing -mmcu=... via gcc ASM_SPEC as well
 	   as .arch ... in the asm output at the same time.  */
 	if (avr_mcu == &default_mcu || avr_mcu->mach == mcu_types[i].mach)
-	  avr_mcu = &mcu_types[i];
+      {
+        specified_mcu.name = mcu_types[i].name;
+        specified_mcu.isa  |= mcu_types[i].isa;
+        specified_mcu.mach = mcu_types[i].mach;
+        avr_mcu = &specified_mcu;
+      }
 	else
 	  as_fatal (_("redefinition of mcu type `%s' to `%s'"),
 		    avr_mcu->name, mcu_types[i].name);
@@ -573,6 +584,9 @@ md_parse_option (int c, char *arg)
     case OPTION_NO_WRAP:
       avr_opt.no_wrap = 1;
       return 1;
+    case OPTION_ISA_RMW:
+      specified_mcu.isa |= AVR_ISA_RMW;
+      return 1;
     }
 
   return 0;

gas/doc/c-avr.texi

@@ -129,6 +129,10 @@ This option disable warnings for skipping two-word instructions.
 @item -mno-wrap
 This option reject @code{rjmp/rcall} instructions with 8K wrap-around.
 
+@cindex @code{-mrmw} command line option, AVR
+@item -mrmw
+Accept Read-Modify-Write (@code{XCH,LAC,LAS,LAT}) instructions.
+
 @end table
 
 

gas/testsuite/gas/avr/avr.exp

@@ -0,0 +1,24 @@
+# Copyright 2014
+# Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+# 
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+# 
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.  
+
+#
+# Some AVR tests
+#
+
+if {[istarget avr-*-*]} {
+    run_dump_tests [lsort [glob -nocomplain $srcdir/$subdir/*.d]]
+}

gas/testsuite/gas/avr/rmw.d

@@ -0,0 +1,23 @@
+#name: AVR RMW instructions
+#as: -mmcu=avrxmega2 -mrmw
+#objdump: -dr --show-raw-insn
+#target: avr-*-*
+
+.*: +file format elf32-avr
+
+Disassembly of section .text:
+
+00000000 <main>:
+   0:	cf 93       	push	r28
+   2:	df 93       	push	r29
+   4:	cd b7       	in	r28, 0x3d	; 61
+   6:	de b7       	in	r29, 0x3e	; 62
+   8:	c4 92       	xch	Z, r12
+   a:	c5 92       	las	Z, r12
+   c:	c6 92       	lac	Z, r12
+   e:	c7 92       	lat	Z, r12
+  10:	80 e0       	ldi	r24, 0x00	; 0
+  12:	90 e0       	ldi	r25, 0x00	; 0
+  14:	df 91       	pop	r29
+  16:	cf 91       	pop	r28
+  18:	08 95       	ret

gas/testsuite/gas/avr/rmw.s

@@ -0,0 +1,32 @@
+	.file	"rmw.s"
+__SP_H__ = 0x3e
+__SP_L__ = 0x3d
+__SREG__ = 0x3f
+__CCP__ = 0x34
+__tmp_reg__ = 0
+__zero_reg__ = 1
+	.text
+.global	main
+	.type	main, @function
+main:
+	push r28
+	push r29
+	in r28,__SP_L__
+	in r29,__SP_H__
+/* prologue: function */
+/* frame size = 0 */
+/* stack size = 2 */
+.L__stack_usage = 2
+/* #APP */
+	xch Z, r12
+	las Z, r12
+	lac Z, r12
+	lat Z, r12
+/* #NOAPP */
+	ldi r24,0
+	ldi r25,0
+/* epilogue start */
+	pop r29
+	pop r28
+	ret
+	.size	main, .-main