nir: add late opt to turn inot/b2f combos back to bcsel

We turn these from bcsel into inot/b2f combos in order for other
optimisation passes to get further. Once we have finished turn
the ones that remain and are used in more than a single expression
back into a bcsel.

On BDW:

total instructions in shared programs: 13060965 -> 13060297 (-0.01%)
instructions in affected programs: 835701 -> 835033 (-0.08%)
helped: 670
HURT: 2

total cycles in shared programs: 256599536 -> 256598006 (-0.00%)
cycles in affected programs: 114655488 -> 114653958 (-0.00%)
helped: 419
HURT: 240

LOST:   0
GAINED: 1

The 2 HURT is because inserting bcsel creates the only use of
const 1.0 in two shaders from tri-of-friendship-and-madness.

Reviewed-by: Jason Ekstrand <[email protected]>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/compiler/nir/nir_search_helpers.h b/src/compiler/nir/nir_search_helpers.h
index 20fdae66e2c..ebb77ae67aa 100644
--- a/src/compiler/nir/nir_search_helpers.h
+++ b/src/compiler/nir/nir_search_helpers.h
@@ -114,4 +114,20 @@ is_zero_to_one(nir_alu_instr *instr, unsigned src, unsigned num_components,
    return true;
 }
 
+static inline bool
+is_used_more_than_once(nir_alu_instr *instr)
+{
+   bool zero_if_use = list_empty(&instr->dest.dest.ssa.if_uses);
+   bool zero_use = list_empty(&instr->dest.dest.ssa.uses);
+
+   if (zero_use && zero_if_use)
+      return false;
+   else if (zero_use && list_is_singular(&instr->dest.dest.ssa.if_uses))
+      return false;
+   else if (zero_if_use && list_is_singular(&instr->dest.dest.ssa.uses))
+      return false;
+
+   return true;
+}
+
 #endif /* _NIR_SEARCH_ */