https://gitlab.freedesktop.org/mesa/mesa/merge_requests/22
This series adds a new optimization pass that tries to replace code
sequences like
if (x < y) {
z = y - x;
...
}
with a sequence like
t = x - y;
if (t < 0) {
z = -t;
...
}
On architectures where the subtract can generate the flags used by the
if-statement, this saves an instruction. It's also possible that moving
an instruction out of the if-statement will allow
nir_opt_peephole_select to convert the whole thing to a bcsel.
Currently only floating point compares and adds are supported. Adding
support for integer will be a challenge due to integer overflow. There
are a couple possible solutions, but they may not apply to all
architectures.
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