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

[Kenneth Graunke]

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

Your patch is probably better, though.  I never understood the point of
pack/unpacking these.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: This is a digitally signed message part.
URL: <https://lists.freedesktop.org/archives/mesa-dev/attachments/20160208/6a410396/attachment.sig>