[Mesa-dev] [PATCH 09/32] i965/fs: Fix fs_inst::regs_written calculation for instructions with scalar dst.

[Francisco Jerez]

Matt Turner <mattst88 at gmail.com> writes:

> On Fri, Feb 6, 2015 at 6:42 AM, Francisco Jerez <currojerez at riseup.net> wrote:
>> Scalar registers are required to have zero stride, fix the
>> regs_written calculation not to assume that the instruction writes
>> zero registers in that case.
>> ---
>>  src/mesa/drivers/dri/i965/brw_fs.cpp | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
>> index 0a82fb7..bafe438 100644
>> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
>> @@ -126,7 +126,8 @@ fs_inst::init(enum opcode opcode, uint8_t exec_size, const fs_reg &dst,
>>     case HW_REG:
>>     case MRF:
>>     case ATTR:
>> -      this->regs_written = (dst.width * dst.stride * type_sz(dst.type) + 31) / 32;
>> +      this->regs_written =
>> +         CEILING(MAX2(dst.width * dst.stride, 1) * type_sz(dst.type), 32);
>
> I sent basically the same patch ("[PATCH 06/10] i965/fs: Consider
> subregister writes to be writing a register.")
>
> I don't really care which gets committed, but I did have to think a
> lot more about yours (and look up what CEILING did) to be sure it did
> the same thing. Maybe you like mine better?

I find the helper function easier to understand and less error-prone
than the open-coded version.  I admit though that the "easier to
understand" part may not be the case for someone that is not familiar
with CEILING(), as its meaning is far from obvious from its name.  Maybe
we could come up with a more descriptive name?
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