Re: [PATCH 0/7] Streamline arithmetic instruction emulation

[Gleb Natapov <gleb@redhat.com>]

On Sat, Dec 22, 2012 at 02:26:50PM +0200, Avi Kivity wrote:
> The current arithmetic instruction emulation is fairly clumsy: after
> decode, each instruction gets a switch (size), and for every size
> we fetch the operands, prepare flags, emulate the instruction, then store
> back the flags and operands.
> 
> This patchset simplifies things by moving everything into common code
> except the instruction itself.  All the pre- and post- processing is
> coded just once.  The per-instrution code looks like:
> 
>   add %bl, %al
>   ret
> 
>   add %bx, %ax
>   ret
> 
>   add %ebx, %eax
>   ret
> 
>   add %rbx, %rax
>   ret
> 
> The savings in size, for the ten instructions converted in this patchset,
> are fairly large:
> 
>    text	   data	    bss	    dec	    hex	filename
>   63724	      0	      0	  63724	   f8ec	arch/x86/kvm/emulate.o.before
>   61268	      0	      0	  61268	   ef54	arch/x86/kvm/emulate.o.after
> 
> - around 2500 bytes.
> 
> Avi Kivity (7):
>   KVM: x86 emulator: framework for streamlining arithmetic opcodes
>   KVM: x86 emulator: Support for declaring single operand fastops
>   KVM: x86 emulator: introduce NoWrite flag
>   KVM: x86 emulator: mark CMP, CMPS, SCAS, TEST as NoWrite
>   KVM: x86 emulator: convert NOT, NEG to fastop
>   KVM: x86 emulator: add macros for defining 2-operand fastop emulation
>   KVM: x86 emulator: convert basic ALU ops to fastop
> 
>  arch/x86/kvm/emulate.c | 215 +++++++++++++++++++++++++++----------------------
>  1 file changed, 120 insertions(+), 95 deletions(-)
> 
Looks good to me.

--
			Gleb.