Re: [Qemu-devel] [PATCH v10.5 01/20] tcg: Allow multiple word entries into the constant pool

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On 17 January 2018 at 16:14, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>> This will be required for storing vector constants.
>>
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>>  tcg/tcg-pool.inc.c | 115 +++++++++++++++++++++++++++++++++++++++++++----------
>>  1 file changed, 93 insertions(+), 22 deletions(-)
>>
>> diff --git a/tcg/tcg-pool.inc.c b/tcg/tcg-pool.inc.c
>> index 8a85131405..0f76e7bee3 100644
>> --- a/tcg/tcg-pool.inc.c
>> +++ b/tcg/tcg-pool.inc.c
>> @@ -22,39 +22,110 @@
>>
>>  typedef struct TCGLabelPoolData {
>>      struct TCGLabelPoolData *next;
>> -    tcg_target_ulong data;
>>      tcg_insn_unit *label;
>> -    intptr_t addend;
>> -    int type;
>> +    int addend  : 32;
>> +    int rtype   : 16;
>> +    int nlong   : 16;
>> +    tcg_target_ulong data[];
>>  } TCGLabelPoolData;
>>
>
> Seems a bit odd to use bitfields for 32 and 16 bit values, but whatever.
> (My default reaction to bitfields is "be suspicious" :-))

I'm guessing this is the same reason as the softfloat re-factor. By
manually forcing stuff into a bitfield the compiler does a better job of
passing multiple structure elements in a single register?

It would be nice if the compiler could spot this itself though.

>
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
>
> thanks
> -- PMM


--
Alex Bennée