Re: [Qemu-devel] [PATCH] tcg: Reduce max TB opcode count

[Richard Henderson]

On 06/15/2018 03:58 AM, Philippe Mathieu-Daudé wrote:
> On 06/15/2018 03:25 AM, Richard Henderson wrote:
>> Also, assert that we don't overflow any of two different offsets into
>> the TB. Both unwind and goto_tb both record a uint16_t for later use.
>>
>> Signed-off-by: Richard Henderson <address@hidden>
>> ---
>>
>> This fixes an arm-softmmu test case forwarded to me by Michael Tsirkin.
>>
>> There is a TB generated from that test case that runs to 7800 opcodes,
>> and compiles to 96k on an x64 host.  This overflows the 16-bit offset
>> in which we record the goto_tb reset offset.  Because of that overflow,
>> we install a jump destination that goes to neverland.  Boom.
>>
>> With this reduced op count, the same TB compiles to about 48k for
>> both x64 and ppc64le hosts, and neither assertion fires.
> 
> Why not keep that comment in the git history, to follow the 8k -> 4k change?
> 
> Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

Will do, thanks.


r~