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Re: [PATCH 3/7] target/arm: Convert A32 coprocessor insns to decodetree


From: Richard Henderson
Subject: Re: [PATCH 3/7] target/arm: Convert A32 coprocessor insns to decodetree
Date: Tue, 4 Aug 2020 19:53:30 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0

On 8/3/20 4:18 AM, Peter Maydell wrote:
> Convert the A32 coprocessor instructions to decodetree.
> 
> Note that this corrects an underdecoding: for the 64-bit access case
> (MRRC/MCRR) we did not check that bits [24:21] were 0b0010, so we
> would incorrectly treat LDC/STC as MRRC/MCRR rather than UNDEFing
> them.
> 
> The decodetree versions of these insns assume the coprocessor
> is in the range 0..7 or 14..15. This is architecturally sensible
> (as per the comments) and OK in practice for QEMU because the only
> uses of the ARMCPRegInfo infrastructure we have that aren't
> for coprocessors 14 or 15 are the pxa2xx use of coprocessor 6.
> We add an assertion to the define_one_arm_cp_reg_with_opaque()
> function to catch any accidental future attempts to use it to
> define coprocessor registers for invalid coprocessors.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  target/arm/a32.decode  | 19 +++++++++++
>  target/arm/helper.c    | 29 +++++++++++++++++
>  target/arm/translate.c | 74 +++++++++++++++++++++++++++++++++++-------
>  3 files changed, 111 insertions(+), 11 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~



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