[Mesa-dev] [PATCH 4/5] nir: Handle large unsigned values in opt_algebraic.

[Ian Romanick]

On 02/08/2016 01:59 PM, Kenneth Graunke wrote:
> On Thursday, February 4, 2016 5:48:00 PM PST Matt Turner wrote:
>> The next patch adds an algebraic rule that uses the constant 0xff00ff00.
>>
>> Without this change, the build fails with
>>
>>    return hex(struct.unpack('I', struct.pack('i', self.value))[0])
>>    struct.error: 'i' format requires -2147483648 <= number <= 2147483647
>>
>> The hex() function handles integers of any size, and assigning a
>> negative value to an unsigned does what we want in C. The pack/unpack is
>> unnecessary (and as we see, buggy).
>> ---
>>  src/compiler/nir/nir_algebraic.py | 5 +----
>>  1 file changed, 1 insertion(+), 4 deletions(-)
>>
>> diff --git a/src/compiler/nir/nir_algebraic.py
>> b/src/compiler/nir/nir_algebraic.py index 77ad35e..2357b57 100644
>> --- a/src/compiler/nir/nir_algebraic.py
>> +++ b/src/compiler/nir/nir_algebraic.py
>> @@ -102,13 +102,10 @@ class Constant(Value):
>>        self.value = val
>>
>>     def __hex__(self):
>> -      # Even if it's an integer, we still need to unpack as an unsigned
>> -      # int.  This is because, without C99, we can only assign to the first
>> -      # element of a union in an initializer.
>>        if isinstance(self.value, (bool)):
>>           return 'NIR_TRUE' if self.value else 'NIR_FALSE'
>>        if isinstance(self.value, (int, long)):
>> -         return hex(struct.unpack('I', struct.pack('i', self.value))[0])
>> +         return hex(self.value)
>>        elif isinstance(self.value, float):
>>           return hex(struct.unpack('I', struct.pack('f', self.value))[0])
>>        else:
> 
> FWIW, I sent a patch to fix this on January 19th which went unreviewed:
> https://lists.freedesktop.org/archives/mesa-dev/2016-January/105387.html

I was going to R-b it...  After you NAKed the second patch in the series
I waited for v2.

> Your patch is probably better, though.  I never understood the point of
> pack/unpacking these.
> 
> 
> 
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> 


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