Re: [Qemu-devel] [PATCH 01/12] target-s390x: Fix wrong argument in call of tcg_gen_shl_i64()

[Alexander Graf]

On 26.05.2011, at 06:56, Stefan Weil wrote:

> Am 26.05.2011 06:32, schrieb Stefan Weil:
>> Am 26.05.2011 00:15, schrieb Alexander Graf:
>>> On 25.05.2011, at 22:25, Stefan Weil wrote:
>>> 
>>>> tcg_gen_shl_i64 needs an argument of type TCGv_i64.
>>>> Using tmp4 needs some additional changes.
>>>> 
>>>> Signed-off-by: Stefan Weil<address@hidden>
>>>> ---
>>>> target-s390x/translate.c |    8 +++++---
>>>> 1 files changed, 5 insertions(+), 3 deletions(-)
>>>> 
>>>> diff --git a/target-s390x/translate.c b/target-s390x/translate.c
>>>> index 8e71df3..3614516 100644
>>>> --- a/target-s390x/translate.c
>>>> +++ b/target-s390x/translate.c
>>>> @@ -2056,7 +2056,6 @@ do_mh:
>>>>            even for very long ones... */
>>>>         tmp = get_address(s, 0, b2, d2);
>>>>         tmp3 = tcg_const_i64(stm_len);
>>>> -        tmp4 = tcg_const_i64(32);
>>>>         for (i = r1;; i = (i + 1) % 16) {
>>>>             switch (op) {
>>>>             case 0x4:
>>>> @@ -2070,7 +2069,9 @@ do_mh:
>>>> #else
>>>>                 tmp2 = tcg_temp_new_i64();
>>>>                 tcg_gen_qemu_ld32u(tmp2, tmp, get_mem_index(s));
>>>> -                tcg_gen_shl_i64(tmp2, tmp2, 4);
>>>> +                tmp4 = tcg_const_i64(4);
>>>> +                tcg_gen_shl_i64(tmp2, tmp2, tmp4);
>>>> +                tcg_temp_free_i64(tmp4);
>>>>                 tcg_gen_ext32u_i64(regs[i], regs[i]);
>>>>                 tcg_gen_or_i64(regs[i], regs[i], tmp2);
>>>> #endif
>>>> @@ -2081,7 +2082,9 @@ do_mh:
>>>>                 break;
>>>>             case 0x26:
>>>>                 tmp2 = tcg_temp_new_i64();
>>>> +                tmp4 = tcg_const_i64(32);
>>> This moves the const inside the loop, which is exactly what I was trying to 
>>> avoid here. The problem is that every new const generated here issues 1 
>>> additional tcg op, which really sums up when there's too many of them. I've 
>>> had the buffer exceed here plenty of times.
>>> 
>>> Alex
>> 
>> I noticed that, too. But adding a tmp5 and generating two const outside the 
>> loop
>> of whom only one or even none is used is also a bad solution.
>> 
>> What about moving the loop inside the switch statement (one loop for every 
>> case)?
>> This does not look nice but looks like the best solution here.
>> 
>> If you prefer a different solution, just omit this part of my patch series.
>> 
>> Grüße, Stefan
> 
> Would it be possible to use tcg_gen_shli_64 / tcg_gen_shri_64 and remove
> tmp4 completely?

That's what I had originally. It basically does exactly the same as the code 
you have patched it to :). Any immediate tcg op internally just generates a 
const tcg var and calls the generic one.


Alex