intel/fs: Emit logical-not of operands on Gen8+

On Gen8+ specifying negation of a logical operation such as AND actually
performs a logical-not.  Take advantage of this to generate fewer
instructions.

v2: Major rebase.  Use nir_src_as_alu_instr.  Fix swizzle handling.

No changes on any pre-Gen8 platform.

Skylake and Broadwell had similar results. (Broadwell shown)
total instructions in shared programs: 15466902 -> 15466274 (<.01%)
instructions in affected programs: 1262953 -> 1262325 (-0.05%)
helped: 682
HURT: 4
helped stats (abs) min: 1 max: 5 x̄: 1.02 x̃: 1
helped stats (rel) min: 0.03% max: 2.40% x̄: 0.18% x̃: 0.04%
HURT stats (abs)   min: 1 max: 62 x̄: 17.50 x̃: 3
HURT stats (rel)   min: 0.03% max: 1.89% x̄: 0.53% x̃: 0.10%
95% mean confidence interval for instructions value: -1.10 -0.73
95% mean confidence interval for instructions %-change: -0.19% -0.15%
Instructions are helped.

total cycles in shared programs: 410996093 -> 410950440 (-0.01%)
cycles in affected programs: 144389048 -> 144343395 (-0.03%)
helped: 519
HURT: 51
helped stats (abs) min: 1 max: 1060 x̄: 104.46 x̃: 140
helped stats (rel) min: 0.01% max: 10.98% x̄: 0.34% x̃: 0.03%
HURT stats (abs)   min: 1 max: 4060 x̄: 167.90 x̃: 22
HURT stats (rel)   min: <.01% max: 8.20% x̄: 0.96% x̃: 0.25%
95% mean confidence interval for cycles value: -97.16 -63.02
95% mean confidence interval for cycles %-change: -0.32% -0.13%
Cycles are helped.

total spills in shared programs: 95311 -> 95329 (0.02%)
spills in affected programs: 881 -> 899 (2.04%)
helped: 0
HURT: 4

total fills in shared programs: 93629 -> 93634 (<.01%)
fills in affected programs: 794 -> 799 (0.63%)
helped: 1
HURT: 2

Reviewed-by: Kenneth Graunke <[email protected]>

2 files changed, 27 insertions, 6 deletions

diff --git a/src/intel/compiler/brw_fs.h b/src/intel/compiler/brw_fs.h
index d39541bab77..df34c69663b 100644
--- a/src/intel/compiler/brw_fs.h
+++ b/src/intel/compiler/brw_fs.h
@@ -390,6 +390,9 @@ private:
                                               nir_alu_instr *instr,
                                               fs_reg *op,
                                               bool need_dest);
+
+   void resolve_inot_sources(const brw::fs_builder &bld, nir_alu_instr *instr,
+                             fs_reg *op);
 };
 
 /**
diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
index ad29351a95c..23b21f1d680 100644
--- a/src/intel/compiler/brw_fs_nir.cpp
+++ b/src/intel/compiler/brw_fs_nir.cpp
@@ -733,6 +733,27 @@ fs_visitor::prepare_alu_destination_and_sources(const fs_builder &bld,
 }
 
 void
+fs_visitor::resolve_inot_sources(const fs_builder &bld, nir_alu_instr *instr,
+                                 fs_reg *op)
+{
+   for (unsigned i = 0; i < 2; i++) {
+      nir_alu_instr *const inot_instr =
+         nir_src_as_alu_instr(&instr->src[i].src);
+
+      if (inot_instr != NULL && inot_instr->op == nir_op_inot &&
+          !inot_instr->src[0].abs && !inot_instr->src[0].negate) {
+         /* The source of the inot is now the source of instr. */
+         prepare_alu_destination_and_sources(bld, inot_instr, &op[i], false);
+
+         assert(!op[i].negate);
+         op[i].negate = true;
+      } else {
+         op[i] = resolve_source_modifiers(op[i]);
+      }
+   }
+}
+
+void
 fs_visitor::nir_emit_alu(const fs_builder &bld, nir_alu_instr *instr)
 {
    struct brw_wm_prog_key *fs_key = (struct brw_wm_prog_key *) this->key;
@@ -1140,22 +1161,19 @@ fs_visitor::nir_emit_alu(const fs_builder &bld, nir_alu_instr *instr)
       break;
    case nir_op_ixor:
       if (devinfo->gen >= 8) {
-         op[0] = resolve_source_modifiers(op[0]);
-         op[1] = resolve_source_modifiers(op[1]);
+         resolve_inot_sources(bld, instr, op);
       }
       bld.XOR(result, op[0], op[1]);
       break;
    case nir_op_ior:
       if (devinfo->gen >= 8) {
-         op[0] = resolve_source_modifiers(op[0]);
-         op[1] = resolve_source_modifiers(op[1]);
+         resolve_inot_sources(bld, instr, op);
       }
       bld.OR(result, op[0], op[1]);
       break;
    case nir_op_iand:
       if (devinfo->gen >= 8) {
-         op[0] = resolve_source_modifiers(op[0]);
-         op[1] = resolve_source_modifiers(op[1]);
+         resolve_inot_sources(bld, instr, op);
       }
       bld.AND(result, op[0], op[1]);
       break;