Re: [Qemu-devel] [PATCH 2/3] tcg: Use "unspecified behaviour" for shifts

[Peter Maydell]

On 18 March 2014 15:48, Richard Henderson <address@hidden> wrote:
> Change the definition such that shifts are not allowed to crash
> for any input.
>
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  tcg/README | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/tcg/README b/tcg/README
> index f178212..431cee7 100644
> --- a/tcg/README
> +++ b/tcg/README
> @@ -36,6 +36,12 @@ or a memory location which is stored in a register outside 
> QEMU TBs
>  A TCG "basic block" corresponds to a list of instructions terminated
>  by a branch instruction.
>
> +An operation with "undefined behavior" may result in a crash.
> +
> +An operation with "unspecified behaviour" shall not crash.  However,

no 'u' would be consistent with the US spelling elsewhere.

Otherwise
Reviewed-by: Peter Maydell <address@hidden>


Incidentally, are deposit ops with bogus pos and len
undefined or unspecified behavior? (And is deposit of
64 bits to bit 0 allowed?)

thanks
-- PMM