[Mesa-dev] [PATCH] softpipe: Do round-to-even, not round-up.

[Brian Paul]

On 06/25/2012 12:49 AM, Olivier Galibert wrote:
> On Fri, May 18, 2012 at 08:55:39AM -0600, Brian Paul wrote:
>> In any case, I think this function could be moved into u_math.c so it
>> could be used elsewhere.
> [...]
>> I was looking at the GLSL round() and roundEven() functions.  The GLSL
>> spec says round() can use whatever method is fastest.  But in
>> builtin_functions.cpp the round() function is implemented in terms of
>> the round_even builtin.  It seems to me that we should have a generic
>> 'round' builtin function and separate TGSI_ROUND and TGSI_ROUND_EVEN
>> opcodes so that drivers can really have the option of using a
>> faster/looser round function.
>
> I've tried doing that.  I've moved the function to u_math.c, then made
> src/glsl/ir_constant_expression.cpp use it.  That blew up.
>
> If I compile with scons, I get:
>    Linking build/linux-x86_64-debug/glsl/builtin_compiler ...
> build/linux-x86_64-debug/glsl/ir_constant_expression.o: In function `dot':
> /home/galibert/X/work/mesa-play/src/glsl/ir_constant_expression.cpp:47: undefined reference to `_debug_assert_fail'
> [...]
> /home/galibert/X/work/mesa-play/src/glsl/ir_constant_expression.cpp:265: undefined reference to `ieee754_fp32_round_half_to_even'
> [etc]
>
> If I compile with autoconf/make I get:
> ir_constant_expression.cpp:42:25: fatal error: util/u_math.h: No such file or directory
>
> So at that point src/glsl and src/gallium are not supposed to meet
> each other.  And changing that is not a responsability I feel like
> taking.  Any advice?

For the time being (until we can do the code sharing that Jose 
mentioned) you can just duplicate the code in imports.[ch]

-Brian