[Mesa-dev] [PATCH 3/3] nir: Add a bunch of b2[if] optimizations

[Jason Ekstrand]

The b2f and b2i conversions always produce zero or one which are both
representable in every type and size.  Since b2i and b2f support all bit
sizes, we can just get rid of the conversion opcode.

total instructions in shared programs: 15089335 -> 15084368 (-0.03%)
instructions in affected programs: 212564 -> 207597 (-2.34%)
helped: 896
HURT: 0

total cycles in shared programs: 369831123 -> 369826267 (<.01%)
cycles in affected programs: 2008647 -> 2003791 (-0.24%)
helped: 693
HURT: 216
---
 src/compiler/nir/nir_opt_algebraic.py | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 422a8794d38..cc747250ba5 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -751,6 +751,23 @@ for left, right in itertools.combinations_with_replacement(invert.keys(), 2):
    optimizations.append((('inot', ('iand(is_used_once)', (left, a, b), (right, c, d))),
                          ('ior', (invert[left], a, b), (invert[right], c, d))))
 
+# Optimize x2yN(b2x(x)) -> b2y
+optimizations.append((('f2b', ('b2f', a)), a))
+optimizations.append((('i2b', ('b2i', a)), a))
+for x, y in itertools.product(['f', 'u', 'i'], ['f', 'u', 'i']):
+   if x != 'f' and y != 'f' and x != y:
+      continue
+
+   b2x = 'b2f' if x == 'f' else 'b2i'
+   b2y = 'b2f' if y == 'f' else 'b2i'
+
+   for N in [8, 16, 32, 64]:
+      if y == 'f' and N == 8:
+         continue
+
+      x2yN = '{}2{}{}'.format(x, y, N)
+      optimizations.append(((x2yN, (b2x, a)), (b2y, a)))
+
 def fexp2i(exp, bits):
    # We assume that exp is already in the right range.
    if bits == 32:
-- 
2.19.1