Reviewed-by: Ian Romanick <ian.d.roman...@intel.com>
On 12/22/2016 01:54 PM, Jason Ekstrand wrote:
> This sequence shows up The Talos Principal, at least under Vulkan,
> and prevents loop analysis from properly computing trip counts in a
> few loops.
> ---
> src/compiler/nir/nir_opt_algebraic.py | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/src/compiler/nir/nir_opt_algebraic.py
> b/src/compiler/nir/nir_opt_algebraic.py
> index 698ac67..ff10d70 100644
> --- a/src/compiler/nir/nir_opt_algebraic.py
> +++ b/src/compiler/nir/nir_opt_algebraic.py
> @@ -464,6 +464,14 @@ def bitfield_reverse(u):
>
> optimizations += [(bitfield_reverse('x@32'), ('bitfield_reverse', 'x'))]
>
> +# For any float comparison operation, "cmp", if you have "a == a && a cmp b"
> +# then the "a == a" is redundant because it's equivalent to "a is not NaN"
> +# and, if a is a NaN then the second comparison will fail anyway.
> +for op in ['flt', 'fge', 'feq']:
> + optimizations += [
> + (('iand', ('feq', a, a), (op, a, b)), (op, a, b)),
> + (('iand', ('feq', a, a), (op, b, a)), (op, b, a)),
> + ]
>
> # Add optimizations to handle the case where the result of a ternary is
> # compared to a constant. This way we can take things like
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