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Re: [PATCH 3/9] x86: correct MPX insn w/o base or index encoding in 16-bit mode
On 04.03.2020 12:45, H.J. Lu wrote:
> On Wed, Mar 4, 2020 at 1:38 AM Jan Beulich <jbeulich@suse.com> wrote:
>> --- a/gas/config/tc-i386.c
>> +++ b/gas/config/tc-i386.c
>> @@ -10297,6 +10297,21 @@ i386_addressing_mode (void)
>>
>> if (i.prefix[ADDR_PREFIX])
>> addr_mode = flag_code == CODE_32BIT ? CODE_16BIT : CODE_32BIT;
>> + else if (flag_code == CODE_16BIT
>> + && current_templates->start->cpu_flags.bitfield.cpumpx
>> + /* Avoid replacing the "16-bit addressing not allowed" diagnostic
>> + from md_assemble() by "is not a valid base/index expression"
>> + when there is a base and/or index. */
>> + && !i.types[this_operand].bitfield.baseindex)
>> + {
>> + /* MPX insn memory operands with neither base nor index must be forced
>> + to use 32-bit addressing in 16-bit mode. */
>> + addr_mode = CODE_32BIT;
>> + i.prefix[ADDR_PREFIX] = ADDR_PREFIX_OPCODE;
>> + ++i.prefixes;
>> + gas_assert (!i.types[this_operand].bitfield.disp16);
>> + gas_assert (!i.types[this_operand].bitfield.disp32);
>> + }
>> else
>> {
>
> Since MPX isn't available in 16-bit mode, should they be disallowed?
How is it not available? As per my understanding, one just needs
to use 32-bit addressing.
> Given that MPX has been deprecated, I prefer an error here.
The use of "here" is confusing - just for the broken case (no
base/index), or for MPX insns in general? (Asking just in case
my understanding expressed above is wrong.)
Jan