This fixes the aarch64 assembler so that it will generate error messages when

a syntax error is detected in an optional operand.

  * config/tc-aarch64.c (END_OF_INSN): New macro.
  (parse_operands): Handle operand given and be in wrong
  format when operand is optional.

  * gas/aarch64/diagnostic.s: New test patterns.
  * gas/aarch64/diagnostic.l: Likewise.

gas/ChangeLog

@@ -1,3 +1,9 @@
+2014-06-16  Jiong Wang  <jiong.wang@arm.com>
+
+	* config/tc-aarch64.c (END_OF_INSN): New macro.
+	(parse_operands): Handle operand given and in wrong format when
+	operand is optional.
+
 2014-06-16  Alan Modra  <amodra@gmail.com>
 
 	* write.h (subsegs_finish): Delete declaration.

gas/config/tc-aarch64.c

@@ -42,6 +42,8 @@
 
 #define streq(a, b)	      (strcmp (a, b) == 0)
 
+#define END_OF_INSN '\0'
+
 static aarch64_feature_set cpu_variant;
 
 /* Variables that we set while parsing command-line options.  Once all
@@ -5302,6 +5304,37 @@ failure:
       if (! backtrack_pos)
 	goto parse_operands_return;
 
+      {
+	/* We reach here because this operand is marked as optional, and
+	   either no operand was supplied or the operand was supplied but it
+	   was syntactically incorrect.  In the latter case we report an
+	   error.  In the former case we perform a few more checks before
+	   dropping through to the code to insert the default operand.  */
+
+	char *tmp = backtrack_pos;
+	char endchar = END_OF_INSN;
+
+	if (i != (aarch64_num_of_operands (opcode) - 1))
+	  endchar = ',';
+	skip_past_char (&tmp, ',');
+
+	if (*tmp != endchar)
+	  /* The user has supplied an operand in the wrong format.  */
+	  goto parse_operands_return;
+
+	/* Make sure there is not a comma before the optional operand.
+	   For example the fifth operand of 'sys' is optional:
+
+	     sys #0,c0,c0,#0,  <--- wrong
+	     sys #0,c0,c0,#0   <--- correct.  */
+	if (comma_skipped_p && i && endchar == END_OF_INSN)
+	  {
+	    set_fatal_syntax_error
+	      (_("unexpected comma before the omitted optional operand"));
+	    goto parse_operands_return;
+	  }
+      }
+
       /* Reaching here means we are dealing with an optional operand that is
 	 omitted from the assembly line.  */
       gas_assert (optional_operand_p (opcode, i));
@@ -5312,15 +5345,6 @@ failure:
       str = backtrack_pos;
       backtrack_pos = 0;
 
-      /* If this is the last operand that is optional and omitted, but without
-	 the presence of a comma.  */
-      if (i && comma_skipped_p && i == aarch64_num_of_operands (opcode) - 1)
-	{
-	  set_fatal_syntax_error
-	    (_("unexpected comma before the omitted optional operand"));
-	  goto parse_operands_return;
-	}
-
       /* Clear any error record after the omitted optional operand has been
 	 successfully handled.  */
       clear_error ();

gas/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2014-06-16  Jiong Wang  <jiong.wang@arm.com>
+
+	* gas/aarch64/diagnostic.s: Add new test patterns.
+	* gas/aarch64/diagnostic.l: Update expected diagnostic output.
+
 2014-06-16  Alan Modra  <amodra@gmail.com>
 
 	* gas/elf/bad-group.s: Use %function.

gas/testsuite/gas/aarch64/diagnostic.l

@@ -14,7 +14,7 @@
 [^:]*:16: Error: immediate value out of range 0 to 31 at operand 2 -- `ccmp x0,-1,10,le'
 [^:]*:17: Error: extraneous register at operand 2 -- `tlbi alle3is,x0'
 [^:]*:18: Error: missing register at operand 2 -- `tlbi vaale1is'
-[^:]*:19: Error: unexpected characters following instruction at operand 1 -- `tlbi vaale1is x0'
+[^:]*:19: Error: comma expected between operands at operand 2 -- `tlbi vaale1is x0'
 [^:]*:20: Error: immediate value out of range 0 to 1 at operand 1 -- `msr spsel,3'
 [^:]*:21: Error: immediate value out of range 1 to 64 at operand 3 -- `fcvtzu x15,d31,#66'
 [^:]*:22: Error: immediate value out of range 1 to 32 at operand 3 -- `scvtf s0,w0,33'
@@ -97,3 +97,10 @@
 [^:]*:99: Error: operand 3 should be one of the standard conditions, excluding AL and NV. -- `cinc w0,w1,nv'
 [^:]*:100: Error: operand 2 should be one of the standard conditions, excluding AL and NV. -- `cset w0,al'
 [^:]*:101: Error: operand 2 should be one of the standard conditions, excluding AL and NV. -- `cset w0,nv'
+[^:]*:104: Error: operand 1 should be an integer register -- `ret lr'
+[^:]*:105: Error: operand 1 should be an integer register -- `ret kk'
+[^:]*:106: Error: immediate operand required at operand 1 -- `clrex x0'
+[^:]*:107: Error: immediate operand required at operand 1 -- `clrex w0'
+[^:]*:108: Error: constant expression required at operand 1 -- `clrex kk'
+[^:]*:109: Error: operand 5 should be an integer register -- `sys #0,c0,c0,#0,kk'
+[^:]*:110: Error: unexpected comma before the omitted optional operand at operand 5 -- `sys #0,c0,c0,#0,'

gas/testsuite/gas/aarch64/diagnostic.s

@@ -99,3 +99,12 @@
 	cinc	w0, w1, nv
 	cset	w0, al
 	cset	w0, nv
+
+	# test diagnostic info on optional operand
+	ret	lr
+	ret	kk
+	clrex	x0
+	clrex	w0
+	clrex	kk
+	sys	#0, c0, c0, #0, kk
+	sys	#0, c0, c0, #0,