[PATCH 10/10] x86: correct VFPCLASSP{S,D} operand size handling

Jan Beulich jbeulich@suse.com
Wed Aug 7 08:29:00 GMT 2019

On 06.08.2019 23:11,  H.J. Lu  wrote:
> On Tue, Aug 6, 2019 at 7:29 AM Jan Beulich <jbeulich@suse.com> wrote:
>> With AVX512VL disabled (e.g. when writing code for the Knights family
>> of processors) these insns aren't ambiguous when used with a memory
>> source, and hence should be accepted without suffix or operand size
>> specifier. When AVX512VL is enabled, to be consistent with this as
>> well as other ambiguous operand size handling it seems better to just
>> wanrn about the ambiguity in AT&T mode, and still default to 512-bit
>> operands (on the assumption that the code may have been written without
>> AVX512VL in mind yet).
>> gas/
>> 2019-08-XX  Jan Beulich  <jbeulich@suse.com>
>>          * config/tc-i386.c (avx512): New (at file scope), moved from
>>          (check_VecOperands): ... here.
>>          (process_suffix): Add [XYZ]MMword operand size handling.
>>          * testsuite/gas/i386/noavx512-2.s, testsuite/gas/i386/noreg16.s,
>>          testsuite/gas/i386/noreg32.s, testsuite/gas/i386/noreg64.s: Add
>>          VFPCLASS tests.
>>          * testsuite/gas/i386/noavx512-2.l, testsuite/gas/i386/noreg16.d,
>>          testsuite/gas/i386/noreg16.l, testsuite/gas/i386/noreg32.d,
>>          testsuite/gas/i386/noreg32.l, testsuite/gas/i386/noreg64.d,
>>          testsuite/gas/i386/noreg64.l: Adjust expectations.
>> opcodes/
>> 2019-08-XX  Jan Beulich  <jbeulich@suse.com>
>>          * i386-opc.tbl (vfpclasspd, vfpclassps): Add Unspecified.
>>          * i386-tbl.h: Re-generate.
> We should keep the suffix even if AVX512VL isn't enabled so that
> we don't need to check if AVX512VL isn't enabled to interpret the
> instruction.

But that's wrong (and fixing this is the whole point of this patch).
As you've said elsewhere, unambiguous (SIMD in particular) insns
should not require any use of suffixes.


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