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.
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