[PATCH] gas: sparc: allow ASR registers in the 0..31 range in V9 and later

[jose dot marchesi at oracle dot com (Jose E. Marchesi)]

In the V9 (and later) versions of the SPARC specification, the section
C.1.1 "Register Names" specifies that:
    
    "asr_reg.  An asr_reg is an Ancillary State Register name.  It may have
     one of the following values:
    
      %asr16-%asr31"
    
The rationale of having this restriction was that the registers from 16
to 31 are reserved to implementations, and are therefore "non-V9".  It
also assumes that the existing ASR registers in the range 0..31 will
have their own names such as %y, that can be used to access such
registers.
    
The Solaris assembler is lax and allows to assembly instructions
referring to %asr0 to %asr31.  This patch makes the GNU assembler to
mimic that behavior.

Rationale for the change:
- When a new ASR register is introduced, such as %mcdper (%asr14), there
  is a transition period when the new register name is not recognized by
  the released GAS.  Software developed in that period can now use
  %asr14 and thus not need the latest assembler, nor ugly .byte hacks.

- This is a pure syntax issue: the instruction assembled from %asrN and
  %NAME are exactly the same, and valid SPARC instructions provided N
  corresponds to a valid ASR.
  
- The above mentioned restriction in section C.1.1 of the SPARC
  specification is going to be modified in future editions to allow the
  full range %asr0-%asr31 in the assembly syntax.

- The restriction, as currently implemented in GAS, doesn't work anyway:
  as the `current_architecture' is bumped when instructions requiring a
  later architecture are processed, in the following program only the
  second `rd' instruction will trigger the error:

  rd %asr14,%g1  ;; current arch is V6 => no error raised
  ldx [%g1],%g1  ;; arch bumped to V9
  rd %asr14,%g2  ;; error: %asr register must be in the range %asr16..%asr31

Tested in both sparcv9-*-linux-gnu and sparc64-*-linux-gnu.
No regressions.

Ok to commit?


diff --git a/gas/ChangeLog b/gas/ChangeLog
index 24cf393..9bd9682 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,8 @@
+2016-03-22  Jose E. Marchesi  <jose.marchesi@oracle.com>
+
+	* config/tc-sparc.c (sparc_ip): Remove the V9 restriction on ASR
+	registers to be in the 16..31 range.
+
 2016-03-22  Alan Modra  <amodra@gmail.com>
 
 	* write.c (record_alignment): Revert 2016-02-18 change.
diff --git a/gas/config/tc-sparc.c b/gas/config/tc-sparc.c
index cac5d18..b70c914 100644
--- a/gas/config/tc-sparc.c
+++ b/gas/config/tc-sparc.c
@@ -1841,22 +1841,11 @@ sparc_ip (char *str, const struct sparc_opcode **pinsn)
 			  ++s;
 			}
 
-		      if (current_architecture >= SPARC_OPCODE_ARCH_V9)
-			{
-			  if (num < 16 || 31 < num)
-			    {
-			      error_message = _(": asr number must be between 16 and 31");
-			      goto error;
-			    }
-			}
-		      else
-			{
-			  if (num < 0 || 31 < num)
-			    {
-			      error_message = _(": asr number must be between 0 and 31");
-			      goto error;
-			    }
-			}
+                      if (num < 0 || 31 < num)
+                        {
+                          error_message = _(": asr number must be between 0 and 31");
+                          goto error;
+                        }
 
 		      opcode |= (*args == 'M' ? RS1 (num) : RD (num));
 		      continue;