lima: ppir: duplicate fneg and fabs if its source is an intrinsic

fneg and fabs are folded later in ppir, but having them in nir as a
separate instructions prevents duplicate_intrinsics pass from duplicating
load_input and load_uniform. Duplicate fneg and fabs, so subsequent
duplicate_intrinsic pass can duplicate the loads

shader-db:

total instructions in shared programs: 27698 -> 27675 (-0.08%)
instructions in affected programs: 2752 -> 2729 (-0.84%)
helped: 21
HURT: 2
helped stats (abs) min: 1 max: 4 x̄: 1.19 x̃: 1
helped stats (rel) min: 0.38% max: 6.67% x̄: 2.75% x̃: 0.75%
HURT stats (abs)   min: 1 max: 1 x̄: 1.00 x̃: 1
HURT stats (rel)   min: 1.89% max: 1.89% x̄: 1.89% x̃: 1.89%
95% mean confidence interval for instructions value: -1.39 -0.61
95% mean confidence interval for instructions %-change: -3.67% -1.03%
Instructions are helped.

total loops in shared programs: 2 -> 2 (0.00%)
loops in affected programs: 0 -> 0
helped: 0
HURT: 0

total spills in shared programs: 372 -> 368 (-1.08%)
spills in affected programs: 27 -> 23 (-14.81%)
helped: 4
HURT: 0

total fills in shared programs: 1224 -> 1205 (-1.55%)
fills in affected programs: 81 -> 62 (-23.46%)
helped: 4
HURT: 0

LOST:   0
GAINED: 0

Reviewed-by: Erico Nunes <nunes.erico@gmail.com>
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33569>

src/gallium/drivers/lima/ir/lima_ir.h

@@ -72,6 +72,7 @@ bool lima_nir_split_loads(nir_shader *shader);
 void lima_nir_duplicate_load_consts(nir_shader *shader);
 void lima_nir_duplicate_load_inputs(nir_shader *shader);
 void lima_nir_duplicate_load_uniforms(nir_shader *shader);
+void lima_nir_duplicate_modifiers(nir_shader *shader);
 
 bool lima_nir_lower_txp(nir_shader *shader);
 

src/gallium/drivers/lima/ir/lima_nir_duplicate_modifiers.c

@@ -0,0 +1,129 @@
+/*
+ * Copyright (c) 2025 Lima Project
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+#include "lima_ir.h"
+
+static bool
+lima_nir_duplicate_modifier(nir_builder *b, nir_alu_instr *alu,
+                             nir_op op)
+{
+   nir_alu_instr *last_dupl = NULL;
+   nir_instr *last_parent_instr = NULL;
+
+   nir_foreach_use_safe(use_src, &alu->def) {
+      nir_alu_instr *dupl;
+
+      if (last_parent_instr != nir_src_parent_instr(use_src)) {
+         /* if ssa use, clone for the target block */
+         b->cursor = nir_before_instr(nir_src_parent_instr(use_src));
+         dupl = nir_alu_instr_clone(b->shader, alu);
+         dupl->instr.pass_flags = 1;
+         nir_builder_instr_insert(b, &dupl->instr);
+      }
+      else {
+         dupl = last_dupl;
+      }
+
+      nir_src_rewrite(use_src, &dupl->def);
+      last_parent_instr = nir_src_parent_instr(use_src);
+      last_dupl = dupl;
+   }
+
+   last_dupl = NULL;
+   nir_if *last_parent_if = NULL;
+
+   nir_foreach_if_use_safe(use_src, &alu->def) {
+      nir_alu_instr *dupl;
+      nir_if *nif = nir_src_parent_if(use_src);
+
+      if (last_parent_if != nif) {
+         /* if 'if use', clone where it is */
+         b->cursor = nir_before_instr(&alu->instr);
+         dupl = nir_alu_instr_clone(b->shader, alu);
+         dupl->instr.pass_flags = 1;
+         nir_builder_instr_insert(b, &dupl->instr);
+      }
+      else {
+         dupl = last_dupl;
+      }
+
+      nir_src_rewrite(&nir_src_parent_if(use_src)->condition, &dupl->def);
+      last_parent_if = nif;
+      last_dupl = dupl;
+   }
+
+   nir_instr_remove(&alu->instr);
+   return true;
+}
+
+static void
+lima_nir_duplicate_modifier_impl(nir_shader *shader, nir_function_impl *impl,
+                                  nir_op op)
+{
+   nir_builder builder = nir_builder_create(impl);
+
+   nir_foreach_block(block, impl) {
+      nir_foreach_instr(instr, block) {
+         instr->pass_flags = 0;
+      }
+
+      nir_foreach_instr_safe(instr, block) {
+         if (instr->type != nir_instr_type_alu)
+            continue;
+
+         nir_alu_instr *alu = nir_instr_as_alu(instr);
+
+         if (alu->op != op)
+            continue;
+
+         if (alu->instr.pass_flags)
+            continue;
+
+         nir_intrinsic_instr *itr = nir_src_as_intrinsic(alu->src[0].src);
+         if (!itr)
+            continue;
+
+         if (itr->intrinsic != nir_intrinsic_load_input &&
+             itr->intrinsic != nir_intrinsic_load_uniform)
+            continue;
+
+         lima_nir_duplicate_modifier(&builder, alu, op);
+      }
+   }
+
+   nir_metadata_preserve(impl, nir_metadata_control_flow);
+}
+
+/* Duplicate load inputs for every user.
+ * Helps by utilizing the load input instruction slots that would
+ * otherwise stay empty, and reduces register pressure. */
+void
+lima_nir_duplicate_modifiers(nir_shader *shader)
+{
+   nir_foreach_function_impl(impl, shader) {
+      lima_nir_duplicate_modifier_impl(shader, impl, nir_op_fneg);
+      lima_nir_duplicate_modifier_impl(shader, impl, nir_op_fabs);
+   }
+}

src/gallium/drivers/lima/lima_program.c

@@ -280,6 +280,7 @@ lima_program_optimize_fs_nir(struct nir_shader *s,
 
    NIR_PASS_V(s, nir_opt_dce); /* clean up any new dead code from vec to movs */
 
+   NIR_PASS_V(s, lima_nir_duplicate_modifiers);
    NIR_PASS_V(s, lima_nir_duplicate_load_uniforms);
    NIR_PASS_V(s, lima_nir_duplicate_load_inputs);
    NIR_PASS_V(s, lima_nir_duplicate_load_consts);

src/gallium/drivers/lima/meson.build

@@ -30,6 +30,7 @@ files_lima = files(
 
   'ir/lima_nir_duplicate_consts.c',
   'ir/lima_nir_duplicate_intrinsic.c',
+  'ir/lima_nir_duplicate_modifiers.c',
   'ir/lima_nir_lower_uniform_to_scalar.c',
   'ir/lima_nir_split_load_input.c',
   'ir/lima_nir_split_loads.c',