Mesa (master): nir: Optimize integer division and modulus with 1

[Ian Romanick]

Module: Mesa
Branch: master
Commit: 4d35683d91e3d61bf14b76d801bf6ae17237e162
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=4d35683d91e3d61bf14b76d801bf6ae17237e162

Author: Ian Romanick <ian.d.romanick at intel.com>
Date:   Wed Oct 19 08:53:10 2016 -0700

nir: Optimize integer division and modulus with 1

The previous power-of-two rules didn't catch idiv (because i965 doesn't
set lower_idiv) and imod cases.  The udiv and umod cases should have
been caught, but I included them for orthogonality.

This fixes silly code observed from compute shaders with local_size_[xy]
= 1.

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98299
Reviewed-by: Jordan Justen <jordan.l.justen at intel.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

---

 src/compiler/nir/nir_opt_algebraic.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 2de8050..82d92f4 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -66,6 +66,10 @@ optimizations = [
 
    (('imul', a, '#b at 32(is_pos_power_of_two)'), ('ishl', a, ('find_lsb', b))),
    (('imul', a, '#b at 32(is_neg_power_of_two)'), ('ineg', ('ishl', a, ('find_lsb', ('iabs', b))))),
+   (('udiv', a, 1), a),
+   (('idiv', a, 1), a),
+   (('umod', a, 1), 0),
+   (('imod', a, 1), 0),
    (('udiv', a, '#b at 32(is_pos_power_of_two)'), ('ushr', a, ('find_lsb', b))),
    (('idiv', a, '#b at 32(is_pos_power_of_two)'), ('imul', ('isign', a), ('ushr', ('iabs', a), ('find_lsb', b))), 'options->lower_idiv'),
    (('idiv', a, '#b at 32(is_neg_power_of_two)'), ('ineg', ('imul', ('isign', a), ('ushr', ('iabs', a), ('find_lsb', ('iabs', b))))), 'options->lower_idiv'),