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Re: [qemu-s390x] [Qemu-devel] [PATCH v1] s390x/tcg: Don't model FP regis

From: David Hildenbrand
Subject: Re: [qemu-s390x] [Qemu-devel] [PATCH v1] s390x/tcg: Don't model FP registers as globals
Date: Mon, 4 Feb 2019 14:30:16 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

On 04.02.19 14:27, Richard Henderson wrote:
> On 1/31/19 2:37 PM, David Hildenbrand wrote:
>> As floating point registers overlay some vector registers and we want
>> to make use of the general tcg_gvec infrastructure that assumes vectors
>> are not stored in globals but in memory, don't model flaoting point
>> registers as globals anymore. This is than similar to how arm handles
>> it.
>> Reading/writing a floating point register means reading/writing memory now.
>> Break up ugly in2_x2() handling that modifies both, in1 and in2 into
>> in1_x2l and in2_x2h. This makes things more readable. Also, in1_x1() is
>> ugly as it touches out/out2, get rid of that and use prep_x1() instead.
>> As we are no longer able to use the original global variables for
>> out/out2, we have to use new temporary variables and write from them to
>> the target registers using wout_ helpers.
>> E.g. an instruction that reads and writes x1 will use
>> - prep_x1 to get the values into out/out2
>> - wout_x1 to write the values from out/out2
>> This special handling is needed for x1 as it is often used along with
>> other inputs, so in1/in2 is already used.
>> Signed-off-by: David Hildenbrand <address@hidden>
>> ---
>>  target/s390x/insn-data.def | 150 ++++++++++++++++++-------------------
>>  target/s390x/translate.c   | 133 +++++++++++++++++++-------------
>>  2 files changed, 158 insertions(+), 125 deletions(-)
> Reviewed-by: Richard Henderson <address@hidden>


I'll probably switch naming of in1_x2l and in2_x2h to

in1_x2h and in2_x2l (will double check, but I guess this is the right
thing to do - high double word always comes first, e.g. in memory).

> r~



David / dhildenb

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