Re: [PATCH 13/20] target/arm: Convert LDR/STR with 12-bit immediate to decodetree

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Peter,

On 2/6/23 17:52, Peter Maydell wrote:
> Convert the LDR and STR instructions which use a 12-bit immediate
> offset to decodetree. We can reuse the existing LDR and STR
> trans functions for these.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/arm/tcg/a64.decode      |  25 ++++++++
>   target/arm/tcg/translate-a64.c | 103 +++++----------------------------
>   2 files changed, 41 insertions(+), 87 deletions(-)
> 
> diff --git a/target/arm/tcg/a64.decode b/target/arm/tcg/a64.decode
> index 4dfb7bbdc2e..c3a6d0b740a 100644
> --- a/target/arm/tcg/a64.decode
> +++ b/target/arm/tcg/a64.decode


> +# Load/store with an unsigned 12 bit immediate, which is scaled by the
> +# element size. The function gets the sz:imm and returns the scaled immediate.
> +%uimm_scaled   10:12 sz:3 !function=uimm_scaled
> +
> +@ldst_uimm      .. ... . .. .. ............ rn:5 rt:5 &ldst_imm unpriv=0 p=0 w=0 imm=%uimm_scaled
> +
> +STR_i           sz:2 111 0 01 00 ............ ..... ..... @ldst_uimm sign=0 ext=0
> +LDR_i           00 111 0 01 01 ............ ..... ..... @ldst_uimm sign=0 ext=1 sz=0
> +LDR_i           01 111 0 01 01 ............ ..... ..... @ldst_uimm sign=0 ext=1 sz=1
> +LDR_i           10 111 0 01 01 ............ ..... ..... @ldst_uimm sign=0 ext=1 sz=2
> +LDR_i           11 111 0 01 01 ............ ..... ..... @ldst_uimm sign=0 ext=0 sz=3
> +LDR_i           00 111 0 01 10 ............ ..... ..... @ldst_uimm sign=1 ext=0 sz=0
> +LDR_i           01 111 0 01 10 ............ ..... ..... @ldst_uimm sign=1 ext=0 sz=1
> +LDR_i           10 111 0 01 10 ............ ..... ..... @ldst_uimm sign=1 ext=0 sz=2
> +LDR_i           00 111 0 01 11 ............ ..... ..... @ldst_uimm sign=1 ext=1 sz=0
> +LDR_i           01 111 0 01 11 ............ ..... ..... @ldst_uimm sign=1 ext=1 sz=1

Why not use "sz:2 111 0 01 sign:1 ext:1", returning false for the
cases not covered?