Mesa (master): nir/i965: add before ffma algebraic opts

[Timothy Arceri]

Module: Mesa
Branch: master
Commit: 7a7ee40c2de01a927d78852b18fc0b93e780df9c
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=7a7ee40c2de01a927d78852b18fc0b93e780df9c

Author: Timothy Arceri <timothy.arceri at collabora.com>
Date:   Fri Jan 13 17:25:11 2017 +1100

nir/i965: add before ffma algebraic opts

This shuffles constants down in the reverse of what the previous
patch does and applies some simpilifications that may be made
possible from doing so.

Shader-db results BDW:

total instructions in shared programs: 12980814 -> 12977822 (-0.02%)
instructions in affected programs: 281889 -> 278897 (-1.06%)
helped: 1231
HURT: 128

total cycles in shared programs: 246562852 -> 246567288 (0.00%)
cycles in affected programs: 11271524 -> 11275960 (0.04%)
helped: 1630
HURT: 1378

V2: mark float opts as inexact

Reviewed-by: Elie Tournier <elie.tournier at collabora.com>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

---

 src/compiler/nir/nir.h                |  1 +
 src/compiler/nir/nir_opt_algebraic.py | 23 +++++++++++++++++++++++
 src/intel/compiler/brw_nir.c          |  6 ++++++
 3 files changed, 30 insertions(+)

diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index ce5b434d56..dbbf26859f 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -2598,6 +2598,7 @@ bool nir_lower_phis_to_regs_block(nir_block *block);
 bool nir_lower_ssa_defs_to_regs_block(nir_block *block);
 
 bool nir_opt_algebraic(nir_shader *shader);
+bool nir_opt_algebraic_before_ffma(nir_shader *shader);
 bool nir_opt_algebraic_late(nir_shader *shader);
 bool nir_opt_constant_folding(nir_shader *shader);
 
diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 974345a17e..fe6e33d313 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -530,6 +530,27 @@ for op in ['flt', 'fge', 'feq', 'fne',
        ('bcsel', 'a', (op, 'd', 'b'), (op, 'd', 'c'))),
    ]
 
+# This section contains "late" optimizations that should be run before
+# creating ffmas and calling regular optimizations for the final time.
+# Optimizations should go here if they help code generation and conflict
+# with the regular optimizations.
+before_ffma_optimizations = [
+   # Propagate constants down multiplication chains
+   (('~fmul(is_used_once)', ('fmul(is_used_once)', 'a(is_not_const)', '#b'), 'c(is_not_const)'), ('fmul', ('fmul', a, c), b)),
+   (('imul(is_used_once)', ('imul(is_used_once)', 'a(is_not_const)', '#b'), 'c(is_not_const)'), ('imul', ('imul', a, c), b)),
+   (('~fadd(is_used_once)', ('fadd(is_used_once)', 'a(is_not_const)', '#b'), 'c(is_not_const)'), ('fadd', ('fadd', a, c), b)),
+   (('iadd(is_used_once)', ('iadd(is_used_once)', 'a(is_not_const)', '#b'), 'c(is_not_const)'), ('iadd', ('iadd', a, c), b)),
+
+   (('~fadd', ('fmul', a, b), ('fmul', a, c)), ('fmul', a, ('fadd', b, c))),
+   (('iadd', ('imul', a, b), ('imul', a, c)), ('imul', a, ('iadd', b, c))),
+   (('~fadd', ('fneg', a), a), 0.0),
+   (('iadd', ('ineg', a), a), 0),
+   (('iadd', ('ineg', a), ('iadd', a, b)), b),
+   (('iadd', a, ('iadd', ('ineg', a), b)), b),
+   (('~fadd', ('fneg', a), ('fadd', a, b)), b),
+   (('~fadd', a, ('fadd', ('fneg', a), b)), b),
+]
+
 # This section contains "late" optimizations that should be run after the
 # regular optimizations have finished.  Optimizations should go here if
 # they help code generation but do not necessarily produce code that is
@@ -556,5 +577,7 @@ late_optimizations = [
 ]
 
 print nir_algebraic.AlgebraicPass("nir_opt_algebraic", optimizations).render()
+print nir_algebraic.AlgebraicPass("nir_opt_algebraic_before_ffma",
+                                  before_ffma_optimizations).render()
 print nir_algebraic.AlgebraicPass("nir_opt_algebraic_late",
                                   late_optimizations).render()
diff --git a/src/intel/compiler/brw_nir.c b/src/intel/compiler/brw_nir.c
index 36ccdf3cb1..3c0a7ced57 100644
--- a/src/intel/compiler/brw_nir.c
+++ b/src/intel/compiler/brw_nir.c
@@ -605,6 +605,12 @@ brw_postprocess_nir(nir_shader *nir, const struct brw_compiler *compiler,
 
    UNUSED bool progress; /* Written by OPT */
 
+
+   do {
+      progress = false;
+      OPT(nir_opt_algebraic_before_ffma);
+   } while (progress);
+
    nir = nir_optimize(nir, compiler, is_scalar);
 
    if (devinfo->gen >= 6) {