[PATCH 2/6] x86: shrink some struct insn_template fields

[H.J. Lu]

On Fri, Mar 26, 2021 at 3:50 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> Now that all base opcodes are only at most 2 bytes in size, shrink its
> template field to just as much. By also shrinking extension_opcode and
> operands to just what they really need, we can free up an entire 32-bit
> slot (plus 4 left bits past the bitfields themselves).
>
> At present this alters sizeof(struct insn_template) only for 32-bit
> builds. In 64-bit builds it instead leaves a padding hole that will
> allow to buffer future growth of other fields (opcode_modifier,
> cpu_flags, operand_types[]).
>
> opcodes/
> 2021-03-XX  Jan Beulich  <jbeulich@suse.com>
>
>         * i386-opc.h (struct insn_template): Shrink base_opcode to 16
>         bits. Shrink extension_opcode to 9 bits. Make it signed. Change
>         value of None. Shrink operands to 3 bits.
> ---
> Code-generation wise it may be better to move the signed
> extension_opcode field last within the containing 32-bit slot.
>

extension_opcode should be next to opcode in template.

-- 
H.J.