On 09/21/2016 10:20 PM, Kenneth Graunke wrote:
> This series reworks the GLSL compiler to inline built-in functions
> immediately, at compile time, rather than importing prototypes and
> linking against an extra shader later on.
> Without this, compile time optimizations are nearly useless. For example,
> trying to use a dot product would generate:
> (call dot ...)
> which would not be turned into
> (expression dot ...)
> until link time, when we actually import the functions, and finally inline.
> Function calls are opaque, and most optimization passes freak out and bail
> when they see them. For example, loop unrolling wouldn't happen at compile
> time at all if a loop contains a built-in function call. This is pretty bad.
> Most built-in functions turn into opcodes, or tiny expression trees.
> It makes sense to simply inline them immediately. Some are larger
> (such as atan). But we eventually inline them all today anyway, so
> I don't see any downside to doing it sooner rather than later.
> Ian recently sent out a patch series that adds a lot of flags for
> "do this optimization anyway, but only for built-ins", in an attempt
> to clean up this (call ...) mess. I think this series should also
> solve those problems, but it deletes a bunch of code, rather than
> adding more code.
That explains why you sent an R-b on a few patches and said nothing
about the rest. I was wondering. :)
> The downside is that the shader-db statistics aren't great today,
> but I don't think there's a lot we can do about that. This changes
> the optimization order significantly. Overall, the difference was
> pretty small, so I think I'm OK with it.
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