nir: recombine nir_op_*sub when lower_sub = false

There are some optimizations which are only implemented for additions
and some optimizations which assume that subtractions have been lowered.
By lowering all subtractions first and later recombine for backends
which prefer this option, we don't have to implement them twice.

This patch also moves lower_negate to nir_opt_algebraic_late() to enable
these optimizations for backends which make use of it.

Reviewed-by: Eric Anholt <[email protected]>
Reviewed-by: Connor Abbott <[email protected]>

1 files changed, 13 insertions, 8 deletions

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 04ce3f0c9bf..bf448303437 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -491,14 +491,14 @@ optimizations.extend([
    (('~fmax', ('fabs', a), 0.0), ('fabs', a)),
    (('~fmin', ('fmax', a, 0.0), 1.0), ('fsat', a), '!options->lower_fsat'),
    (('~fmax', ('fmin', a, 1.0), 0.0), ('fsat', a), '!options->lower_fsat'),
-   (('~fmin', ('fmax', a, -1.0),  0.0), ('fneg', ('fsat', ('fneg', a))), '!options->lower_negate && !options->lower_fsat'),
-   (('~fmax', ('fmin', a,  0.0), -1.0), ('fneg', ('fsat', ('fneg', a))), '!options->lower_negate && !options->lower_fsat'),
+   (('~fmin', ('fmax', a, -1.0),  0.0), ('fneg', ('fsat', ('fneg', a))), '!options->lower_fsat'),
+   (('~fmax', ('fmin', a,  0.0), -1.0), ('fneg', ('fsat', ('fneg', a))), '!options->lower_fsat'),
    (('fsat', ('fsign', a)), ('b2f', ('flt', 0.0, a))),
    (('fsat', ('b2f', a)), ('b2f', a)),
    (('fsat', a), ('fmin', ('fmax', a, 0.0), 1.0), 'options->lower_fsat'),
    (('fsat', ('fsat', a)), ('fsat', a)),
-   (('fsat', ('fneg(is_used_once)', ('fadd(is_used_once)', a, b))), ('fsat', ('fadd', ('fneg', a), ('fneg', b))), '!options->lower_negate && !options->lower_fsat'),
-   (('fsat', ('fneg(is_used_once)', ('fmul(is_used_once)', a, b))), ('fsat', ('fmul', ('fneg', a), b)), '!options->lower_negate && !options->lower_fsat'),
+   (('fsat', ('fneg(is_used_once)', ('fadd(is_used_once)', a, b))), ('fsat', ('fadd', ('fneg', a), ('fneg', b))), '!options->lower_fsat'),
+   (('fsat', ('fneg(is_used_once)', ('fmul(is_used_once)', a, b))), ('fsat', ('fmul', ('fneg', a), b)), '!options->lower_fsat'),
    (('fsat', ('fabs(is_used_once)', ('fmul(is_used_once)', a, b))), ('fsat', ('fmul', ('fabs', a), ('fabs', b))), '!options->lower_fsat'),
    (('fmin', ('fmax', ('fmin', ('fmax', a, b), c), b), c), ('fmin', ('fmax', a, b), c)),
    (('imin', ('imax', ('imin', ('imax', a, b), c), b), c), ('imin', ('imax', a, b), c)),
@@ -940,14 +940,13 @@ optimizations.extend([
    (('~fsub', ('fadd', a, b), b), a),
    (('ussub_4x8', a, 0), a),
    (('ussub_4x8', a, ~0), 0),
-   (('fsub', a, b), ('fadd', a, ('fneg', b)), 'options->lower_sub'),
-   (('isub', a, b), ('iadd', a, ('ineg', b)), 'options->lower_sub'),
-   (('fneg', a), ('fsub', 0.0, a), 'options->lower_negate'),
-   (('ineg', a), ('isub', 0, a), 'options->lower_negate'),
    (('~fadd', a, ('fsub', 0.0, b)), ('fsub', a, b)),
    (('iadd', a, ('isub', 0, b)), ('isub', a, b)),
    (('fabs', ('fsub', 0.0, a)), ('fabs', a)),
    (('iabs', ('isub', 0, a)), ('iabs', a)),
+   # Lower all Subtractions first - they can get recombined later
+   (('fsub', a, b), ('fadd', a, ('fneg', b))),
+   (('isub', a, b), ('iadd', a, ('ineg', b))),
 
    # Propagate negation up multiplication chains
    (('fmul(is_used_by_non_fsat)', ('fneg', a), b), ('fneg', ('fmul', a, b))),
@@ -1445,6 +1444,12 @@ late_optimizations = [
    # optimization loop can prevent other optimizations.
    (('fneg', ('fneg', a)), a),
 
+   # Subtractions get lowered during optimization, so we need to recombine them
+   (('fadd', 'a', ('fneg', 'b')), ('fsub', 'a', 'b'), '!options->lower_sub'),
+   (('iadd', 'a', ('ineg', 'b')), ('isub', 'a', 'b'), '!options->lower_sub'),
+   (('fneg', a), ('fsub', 0.0, a), 'options->lower_negate'),
+   (('ineg', a), ('isub', 0, a), 'options->lower_negate'),
+
    # These are duplicated from the main optimizations table.  The late
    # patterns that rearrange expressions like x - .5 < 0 to x < .5 can create
    # new patterns like these.  The patterns that compare with zero are removed