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Subject: Re: [Qemu-devel] Shifts, ppc[64], xtensa
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To: Max Filippov <jcmvbkbc@gmail.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, qemu-devel@nongnu.org, Aurelien Jarno <aurelien@aurel32.net>

On 09/19/2012 11:30 AM, Peter Maydell wrote:
> ...but on the other hand that ought to work for PPC too, so
> presumably my analysis is wrong somewhere.

It isn't.  It's a target-xtensa bug.

> OP:
>  ---- 0xd0079cff
>  movi_i32 tmp0,$0xd0079cff
>  movi_i32 tmp1,$0x2
>  movi_i32 tmp2,$0x1
>  movi_i32 tmp3,$advance_ccount
>  call tmp3,$0x0,$0,env,tmp2
>  movi_i32 tmp2,$window_check
>  call tmp2,$0x0,$0,env,tmp0,tmp1
>  and_i32 tmp0,ar9,ar8
>  movi_i32 tmp1,$0x0
>  brcond_i32 tmp0,tmp1,eq,$0x0
>  movi_i32 tmp2,$0x0
>  brcond_i32 LCOUNT,tmp2,eq,$0x1
>  movi_i32 tmp2,$0x1
>  sub_i32 LCOUNT,LCOUNT,tmp2
>  movi_i32 tmp2,$0xd0079cf2
>  mov_i32 pc,tmp2
>  goto_tb $0x0
>  exit_tb $0x4a116558
>  set_label $0x1
>  movi_i32 tmp2,$0xd0079d02
>  mov_i32 pc,tmp2
>  exit_tb $0x0
>  set_label $0x0
>  movi_i32 tmp2,$0xd0079d1a
>  mov_i32 pc,tmp2
>  goto_tb $0x1
>  exit_tb $0x4a116559
>  movi_i32 tmp0,$0x0
>  brcond_i32 LCOUNT,tmp0,eq,$0x2
>  movi_i32 tmp0,$0x1
>  sub_i32 LCOUNT,LCOUNT,tmp0
>  movi_i32 tmp0,$0xd0079cf2
>  mov_i32 pc,tmp0
>  goto_tb $0x0
>  exit_tb $0x4a116558
>  set_label $0x2
>  movi_i32 tmp0,$0xd0079d02
>  mov_i32 pc,tmp0
>  exit_tb $0x0

There are two instances of goto_tb $0 in here.
And, amusingly, two checks for LCOUNT.

Since there's no disassembler for xtensa, I'll
leave it to the maintainer to track down from
whence this mistake stems.


r~