Allow for optional operands with non-zero default values.

ISA 2.07 (ie, POWER8) added the rfebb instruction which takes one operand
with the value of either a 0 or 1.  It also defines an extended mnemonic
with no operands (ie, "rfebb") that is supposed to be equivalent to "rfebb 1".
I implemented rfebb's lone operand with PPC_OPERAND_OPTIONAL, but the
problem is, optional operands that are ommitted always default to the
value 0, which is wrong in this case.  I have added support for allowing
non-zero default values by adding an additional flag PPC_OPERAND_OPTIONAL_VALUE
that specifies that the default operand value to be used is stored in the
SHIFT field of the operand field immediately following this one.

This fixes the rfebb issue.  I also fixed the mftb and mfcr instructions
so they use the same mechanism.  This allows us to flag invalid uses of
mfcr where we explicitly pass in a zero FXM value, like the use in a2.[sd].

include/opcode/

	* ppc.h (PPC_OPERAND_OPTIONAL_VALUE): New.
	(ppc_optional_operand_value): New inline function.

opcodes/
	* ppc-dis.h (skip_optional_operands): Use ppc_optional_operand_value.
	* ppc-opc.c (FXM4): Add non-zero optional value.
	(TBR): Likewise.
	(SXL): Likewise.
	(insert_fxm): Handle new default operand value.
	(extract_fxm): Likewise.
	(insert_tbr): Likewise.
	(extract_tbr): Likewise.

gas/
	* config/tc-ppc.c (md_assemble): Use ppc_optional_operand_value.
	Allow for optional operands without insert functions.

gas/testsuite/
	* gas/ppc/power8.d: Fixup rfebb test results.
	* gas/ppc/a2.s: Fix invalid mfcr test.
	* gas/ppc/a2.d: Likewise.

6 files changed, 23 insertions, 6 deletions

diff --git a/gas/ChangeLog b/gas/ChangeLog
index 0a1326e..8d0f28f 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,8 @@
+2015-06-19  Peter Bergner  <bergner@vnet.ibm.com>
+
+	* config/tc-ppc.c (md_assemble): Use ppc_optional_operand_value.
+	Allow for optional operands without insert functions.
+
 2015-06-18  Nick Clifton  <nickc@redhat.com>
 
 	PR gas/18541
diff --git a/gas/config/tc-ppc.c b/gas/config/tc-ppc.c
index 3f6de73..18a11be 100644
--- a/gas/config/tc-ppc.c
+++ b/gas/config/tc-ppc.c
@@ -2752,12 +2752,18 @@ md_assemble (char *str)
       if ((operand->flags & PPC_OPERAND_OPTIONAL) != 0
 	  && skip_optional)
 	{
+	  long val = ppc_optional_operand_value (operand);
 	  if (operand->insert)
 	    {
-	      insn = (*operand->insert) (insn, 0L, ppc_cpu, &errmsg);
+	      insn = (*operand->insert) (insn, val, ppc_cpu, &errmsg);
 	      if (errmsg != (const char *) NULL)
 		as_bad ("%s", errmsg);
 	    }
+	  else if (operand->shift >= 0)
+	    insn |= ((long) val & operand->bitm) << operand->shift;
+	  else
+	    insn |= ((long) val & operand->bitm) >> -operand->shift;
+
 	  if ((operand->flags & PPC_OPERAND_NEXT) != 0)
 	    next_opindex = *opindex_ptr + 1;
 	  continue;
diff --git a/gas/testsuite/ChangeLog b/gas/testsuite/ChangeLog
index 64e8cd7..511dce3 100644
--- a/gas/testsuite/ChangeLog
+++ b/gas/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2015-06-19  Peter Bergner  <bergner@vnet.ibm.com>
+
+	* gas/ppc/power8.d: Fixup rfebb test results.
+	* gas/ppc/a2.s: Fix invalid mfcr test.
+	* gas/ppc/a2.d: Likewise.
+
 2015-06-18  Nick Clifton  <nickc@redhat.com>
 
 	PR gas/18541
diff --git a/gas/testsuite/gas/ppc/a2.d b/gas/testsuite/gas/ppc/a2.d
index aa05cbc..bb60275 100644
--- a/gas/testsuite/gas/ppc/a2.d
+++ b/gas/testsuite/gas/ppc/a2.d
@@ -347,7 +347,7 @@ Disassembly of section \.text:
  4fc:	(7c 00 04 00|00 04 00 7c) 	mcrxr   cr0
  500:	(7d 80 04 00|00 04 80 7d) 	mcrxr   cr3
  504:	(7c 60 00 26|26 00 60 7c) 	mfcr    r3
- 508:	(7c 60 00 26|26 00 60 7c) 	mfcr    r3
+ 508:	(7c 70 20 26|26 20 70 7c) 	mfocrf  r3,2
  50c:	(7c 70 10 26|26 10 70 7c) 	mfocrf  r3,1
  510:	(7c 78 00 26|26 00 78 7c) 	mfocrf  r3,128
  514:	(7d 4a 3a 87|87 3a 4a 7d) 	mfdcr\.  r10,234
diff --git a/gas/testsuite/gas/ppc/a2.s b/gas/testsuite/gas/ppc/a2.s
index 7d0ddc7..ecb8668 100644
--- a/gas/testsuite/gas/ppc/a2.s
+++ b/gas/testsuite/gas/ppc/a2.s
@@ -322,7 +322,7 @@ start:
 	mcrxr	0
 	mcrxr	3
 	mfcr	3
-	mfcr	3,0
+	mfcr	3,0x02
 	mfcr	3,0x01
 	mfcr	3,0x80
 	mfdcr.	10,234
diff --git a/gas/testsuite/gas/ppc/power8.d b/gas/testsuite/gas/ppc/power8.d
index e66951e..61e1cab 100644
--- a/gas/testsuite/gas/ppc/power8.d
+++ b/gas/testsuite/gas/ppc/power8.d
@@ -27,9 +27,9 @@ Disassembly of section \.text:
   44:	(60 42 00 00|00 00 42 60) 	ori     r2,r2,0
   48:	(60 00 00 00|00 00 00 60) 	nop
   4c:	(60 42 00 00|00 00 42 60) 	ori     r2,r2,0
-  50:	(4c 00 01 24|24 01 00 4c) 	rfebb   
-  54:	(4c 00 01 24|24 01 00 4c) 	rfebb   
-  58:	(4c 00 09 24|24 09 00 4c) 	rfebb   1
+  50:	(4c 00 01 24|24 01 00 4c) 	rfebb   0
+  54:	(4c 00 09 24|24 09 00 4c) 	rfebb   
+  58:	(4c 00 09 24|24 09 00 4c) 	rfebb   
   5c:	(4d 95 04 60|60 04 95 4d) 	bctar-  12,4\*cr5\+gt
   60:	(4c 87 04 61|61 04 87 4c) 	bctarl- 4,4\*cr1\+so
   64:	(4d ac 04 60|60 04 ac 4d) 	bctar\+  12,4\*cr3\+lt