[ARM] Allow MOV/MOV.W to accept all possible immediates

[Szabolcs Nagy]

adding the reporter to cc and rich because it broke musl.

On 05/01/17 10:45, Szabolcs Nagy wrote:
> On 01/11/16 12:21, Jiong Wang wrote:
>> Hi,
>>
>>   AArch32 MOV Rd, #imm should accept all immediates which can be encoded into
>> available encoding, A1/A2 for ARM, T1/T2/T3 for Thumb/Thumb2, and MOV is the
>> preferred disassembly syntax.  See latest ARM Architecture Reference Manual for
>> ARMv8-A, section F6.1.108 and for ARMv8-M, section C2.4.89.
>>
>>   The same for MOV.W under Thumb mode.  It should try all possible 32-bit Thumb
>> encoding instead of T2 only.
>>
>>   This patch let MOV/MOV.W accept more immediate formats while their currently
>> supported immediate formats are not affected, so there is no backward compatibility
>> issue, also this patch haven't touched the disassembler.
>>
>>   I think this patch brings GAS closer to ARM Architecture Reference Manual.
>>
>>   OK for master?
>>
>> gas/
>> 2016-11-01  Jiong Wang  <jiong.wang@arm.com>
>>                           * config/tc-arm.c (SBIT_SHIFT): New.
>>         (T2_SBIT_SHIFT): Likewise.
>>         (t32_insn_ok): Return TRUE for MOV in ARMv8-M Baseline.
>>         (md_apply_fix): Try UINT16 encoding when ARM/Thumb modified immediate
>>         encoding failed.
>>         * testsuite/gas/arm/archv6t2-bad.s: New error case.
>>         * testsuite/gas/arm/archv6t2-bad.l: New error match.
>>         * testsuite/gas/arm/archv6t2.s: New testcase.
>>         * testsuite/gas/arm/archv6t2.d: New expected result.
>>         * testsuite/gas/arm/archv8m.s: New testcase
>>         * testsuite/gas/arm/archv8m-base.d: New expected result.
>>         * testsuite/gas/arm/archv8m-main.d: Likewise.
>>         * testsuite/gas/arm/archv8m-main-dsp-1.d: Likewise.
> 
> this caused
> 
> $ cat bug.s
> .syntax unified
> .text
> .arch armv7-a
> 	mov r3,#1
> 
> .arch armv4t
> .eabi_attribute 6,2
> 	bx lr
> 
> $ arm-none-linux-gnueabihf-as -mthumb bug.s
> bug.s: Assembler messages:
> bug.s:4: Error: invalid constant (1) after fixup
> 
> previously this worked, but i'm not sure if the mix
> of .arch directives and .syntax unified is valid here.
>