[Mesa-dev] [PATCH] glsl: Use a separate div_to_mul_rcp lowering flag for integers.

Ian Romanick idr at freedesktop.org
Mon Aug 29 10:50:54 PDT 2011

Hash: SHA1

On 08/28/2011 06:51 PM, Bryan Cain wrote:
> On 08/28/2011 07:38 PM, Eric Anholt wrote:
>> On Sat, 27 Aug 2011 20:18:55 -0700, Kenneth Graunke <kenneth at whitecape.org> wrote:
>>> From: Bryan Cain <bryancain3 at gmail.com>
>>> Using multiply and reciprocal for integer division involves potentially
>>> lossy floating point conversions.  This is okay for older GPUs that
>>> represent integers as floating point, but undesirable for GPUs with
>>> native integer division instructions.
>>> TGSI, for example, has UDIV/IDIV instructions for integer division,
>>> so it makes sense to handle this directly.  Likewise for i965.
>>> Signed-off-by: Bryan Cain <bryancain3 at gmail.com>
>>> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
>>> ---
>>>     case ir_binop_div:
>>> -      if (lowering(DIV_TO_MUL_RCP))
>>> +      if (lowering(INT_DIV_TO_MUL_RCP) && ir->operands[1]->type->is_integer())
>>> +	 int_div_to_mul_rcp(ir);
>>> +      else if (lowering(DIV_TO_MUL_RCP))
>>>  	 div_to_mul_rcp(ir);
>>>        break;
>> Sure looks odd to me for one of these to be checking the type and ther
>> other not.
> It works, though.  If it's not an integer type, it's going to be a float
> type.

Right, but it could be an integer type and !lower(INT_DIV_TO_MUL_RCP).
In which case if lower(DIV_TO_MUL_RCP), do_to_mul_rcp will get called on
an integer type.  Right?
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