Re: [PATCH RESEND] x86/asm/entry/32: simplify pushes of zeroed pt_regs->REGs

From: Andy Lutomirski
Date: Mon May 02 2016 - 14:19:48 EST

On Mon, May 2, 2016 at 7:56 AM, Denys Vlasenko <dvlasenk@xxxxxxxxxx> wrote:
> Use of a temporary R8 register here seems to be unnecessary.
> "push %r8" is a two-byte insn (it needs REX prefix to specify R8),
> "push $0" is two-byte too. It seems just using the latter would be
> no worse.
> Thus, code had an unnecessary "xorq %r8,%r8" insn.
> It probably costs nothing in execution time here since we are probably
> limited by store bandwidth at this point, but still.
> Run-tested under QEMU: 32-bit calls still work:

Acked-by: Andy Lutomirski <luto@xxxxxxxxxx>