Use shader D3D optimization level 0.

Use shader D3D optimization level 0.
Committed: https://code.google.com/p/angleproject/source/detail?r=1562

[vangelis, 2012-12-14 23:33:59]

On 2012/12/14 23:19:29, apatrick1 wrote:

LGTM

[dgkoch, 2012-12-18 14:54:14]

What necessitated turning optimizations off this time?

Would be good to have a record of this somewhere so we know what to test, etc.

[kbr1, 2012-12-19 00:51:04]

On 2012/12/18 14:54:14, dgkoch wrote:
> What necessitated turning optimizations off this time?
> 
> Would be good to have a record of this somewhere so we know what to test, etc.

Some of MapsGL's shaders were causing 10-second-long compiles, and Chrome's GPU
sub-process to be killed. The issue's being tracked under multiple bugs and
email threads within Google so it's unlikely to get lost.

[nicolas, 2012-12-19 14:23:47]

Some complex shaders fail to compile if optimizations are disabled. So perhaps
we should first try compiling without optimizations and if that fails try with
optimizations. This can easily be done by adding another option to the flags
list in ProgramBinary::compileToBinary. By adding a descriptive warning in the
info log, application developers can try to simplify their shaders so it
compiles faster.

[apatrick1, 2012-12-19 18:55:03]

On 2012/12/19 14:23:47, nicolas wrote:
> Some complex shaders fail to compile if optimizations are disabled. So perhaps
> we should first try compiling without optimizations and if that fails try with
> optimizations. This can easily be done by adding another option to the flags
> list in ProgramBinary::compileToBinary. By adding a descriptive warning in the
> info log, application developers can try to simplify their shaders so it
> compiles faster.

It's worse than that. Some complex shaders successfully compile with
optimizations disabled but the resulting binary is invalid. I think we need a
compiler that we can fix when bugs come up.