Mesa (staging/20.1): nir/algebraic: Don't distrubte absolute-value into dot-products

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Module: Mesa
Branch: staging/20.1
Commit: 67fd54b281de6340a758d3db5cae02a8d2da3d93
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=67fd54b281de6340a758d3db5cae02a8d2da3d93

Author: Ian Romanick <ian.d.romanick at intel.com>
Date:   Sat Jun 20 13:48:19 2020 -0700

nir/algebraic: Don't distrubte absolute-value into dot-products

Dot product is multiplication followed by addition, and absolute value
does not distribute into addition.

Only vec4 platforms are affected by this change as scalar-only platforms
never have any of the fdot_replicated instructions.  In the shader-db
results, below, shaders in MANY different applications are affected.
Trine, Doom3, Enemy Territory: Quake Wars, Counter Strike: Global
Offensive, Mad Max, Metro Last Light, and on and on...  I'm really
shocked that there were no test regressions!

All Haswell and earlier platforms had similar results. (Haswell shown)
total instructions in shared programs: 16219743 -> 16219820 (<.01%)
instructions in affected programs: 12171 -> 12248 (0.63%)
helped: 1
HURT: 78
helped stats (abs) min: 1 max: 1 x̄: 1.00 x̃: 1
helped stats (rel) min: 0.78% max: 0.78% x̄: 0.78% x̃: 0.78%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 0.35% max: 2.38% x̄: 0.91% x̃: 1.06%
95% mean confidence interval for instructions value: 0.92 1.03
95% mean confidence interval for instructions %-change: 0.78% 1.00%
Instructions are HURT.

total cycles in shared programs: 538481383 -> 538491045 (<.01%)
cycles in affected programs: 470796 -> 480458 (2.05%)
helped: 149
HURT: 142
helped stats (abs) min: 1 max: 1338 x̄: 71.13 x̃: 4
helped stats (rel) min: 0.06% max: 40.99% x̄: 2.76% x̃: 0.67%
HURT stats (abs)   min: 1 max: 2092 x̄: 142.68 x̃: 12
HURT stats (rel)   min: 0.07% max: 55.38% x̄: 5.07% x̃: 1.07%
95% mean confidence interval for cycles value: -5.28 71.69
95% mean confidence interval for cycles %-change: -0.07% 2.19%
Inconclusive result (value mean confidence interval includes 0).

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
Fixes: 62795475e8f ("nir/algebraic: Distribute source modifiers into instructions")
Closes: #3129
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5581>
(cherry picked from commit 8591adea38b82f973948cd120ffd9f93eb3bd71d)

---

 .pick_status.json                     |  2 +-
 src/compiler/nir/nir_opt_algebraic.py | 14 +++++++-------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/.pick_status.json b/.pick_status.json
index 1bd72fc40c2..7c8e9c9bca5 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -256,7 +256,7 @@
         "description": "nir/algebraic: Don't distrubte absolute-value into dot-products",
         "nominated": true,
         "nomination_type": 1,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": "62795475e8f45f92bb8f467d9e2318fdfdba6297"
     },
diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 8ca3f77905e..8f45b99060b 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -1899,6 +1899,9 @@ distribute_src_mods = [
    (('fdot_replicated4', ('fneg', a), ('fneg', b)), ('fdot_replicated4', a, b)),
    (('fneg', ('fneg', a)), a),
 
+   (('fneg', ('fmul(is_used_once)', a, b)), ('fmul', ('fneg', a), b)),
+   (('fabs', ('fmul(is_used_once)', a, b)), ('fmul', ('fabs', a), ('fabs', b))),
+
    (('fneg', ('ffma(is_used_once)', a, b, c)), ('ffma', ('fneg', a), b, ('fneg', c))),
    (('fneg', ('flrp(is_used_once)', a, b, c)), ('flrp', ('fneg', a), ('fneg', b), c)),
    (('fneg', ('fadd(is_used_once)', a, b)), ('fadd', ('fneg', a), ('fneg', b))),
@@ -1908,21 +1911,18 @@ distribute_src_mods = [
    (('fneg', ('fmin(is_used_once)', a, b)), ('fmax', ('fneg', a), ('fneg', b))),
    (('fneg', ('fmax(is_used_once)', a, b)), ('fmin', ('fneg', a), ('fneg', b))),
 
+   (('fneg', ('fdot_replicated2(is_used_once)', a, b)), ('fdot_replicated2', ('fneg', a), b)),
+   (('fneg', ('fdot_replicated3(is_used_once)', a, b)), ('fdot_replicated3', ('fneg', a), b)),
+   (('fneg', ('fdot_replicated4(is_used_once)', a, b)), ('fdot_replicated4', ('fneg', a), b)),
+
    # fdph works mostly like fdot, but to get the correct result, the negation
    # must be applied to the second source.
    (('fneg', ('fdph_replicated(is_used_once)', a, b)), ('fdph_replicated', a, ('fneg', b))),
-   (('fabs', ('fdph_replicated(is_used_once)', a, b)), ('fdph_replicated', ('fabs', a), ('fabs', b))),
 
    (('fneg', ('fsign(is_used_once)', a)), ('fsign', ('fneg', a))),
    (('fabs', ('fsign(is_used_once)', a)), ('fsign', ('fabs', a))),
 ]
 
-for op in ['fmul', 'fdot_replicated2', 'fdot_replicated3', 'fdot_replicated4']:
-   distribute_src_mods.extend([
-       (('fneg', (op + '(is_used_once)', a, b)), (op, ('fneg', a), b)),
-       (('fabs', (op + '(is_used_once)', a, b)), (op, ('fabs', a), ('fabs', b))),
-   ])
-
 print(nir_algebraic.AlgebraicPass("nir_opt_algebraic", optimizations).render())
 print(nir_algebraic.AlgebraicPass("nir_opt_algebraic_before_ffma",
                                   before_ffma_optimizations).render())