Mesa (master): vc4: Enable the nir_opt_algebraic_late() pass.

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Module: Mesa
Branch: master
Commit: d54ae70ee775bb530e7ff35009b982eff01151b0
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=d54ae70ee775bb530e7ff35009b982eff01151b0

Author: Eric Anholt <eric at anholt.net>
Date:   Thu Sep 26 11:03:46 2019 -0700

vc4: Enable the nir_opt_algebraic_late() pass.

Upcoming changes to sub optimization will make this pass required.  Over
the course of that series, we see uniforms +.46%, instructions -.24%
(seems like a fine tradeoff -- uniforms are 1/2 the size of instructions
as far as cache occupancy)

Reviewed-by: Daniel Schürmann <daniel at schuermann.dev>
Reviewed-by: Connor Abbott <cwabbott0 at gmail.com>

---

 src/gallium/drivers/vc4/vc4_program.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/gallium/drivers/vc4/vc4_program.c b/src/gallium/drivers/vc4/vc4_program.c
index e5f7aa31b0e..7d88444c673 100644
--- a/src/gallium/drivers/vc4/vc4_program.c
+++ b/src/gallium/drivers/vc4/vc4_program.c
@@ -2335,6 +2335,21 @@ vc4_shader_ntq(struct vc4_context *vc4, enum qstage stage,
 
         vc4_optimize_nir(c->s);
 
+        /* Do late algebraic optimization to turn add(a, neg(b)) back into
+         * subs, then the mandatory cleanup after algebraic.  Note that it may
+         * produce fnegs, and if so then we need to keep running to squash
+         * fneg(fneg(a)).
+         */
+        bool more_late_algebraic = true;
+        while (more_late_algebraic) {
+                more_late_algebraic = false;
+                NIR_PASS(more_late_algebraic, c->s, nir_opt_algebraic_late);
+                NIR_PASS_V(c->s, nir_opt_constant_folding);
+                NIR_PASS_V(c->s, nir_copy_prop);
+                NIR_PASS_V(c->s, nir_opt_dce);
+                NIR_PASS_V(c->s, nir_opt_cse);
+        }
+
         NIR_PASS_V(c->s, nir_lower_bool_to_int32);
 
         NIR_PASS_V(c->s, nir_convert_from_ssa, true);