nir: add nir_inline_sysval pass

a bunch of drivers have versions of this, might as well make a common one.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Marek Olšák <maraeo@gmail.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Mary Guillemard <mary.guillemard@collabora.com>
Reviewed-by: John Anthony <john.anthony@arm.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/36516>

src/compiler/nir/meson.build

@@ -126,6 +126,7 @@ else
   'nir_gather_xfb_info.c',
   'nir_opt_group_loads.c',
   'nir_gs_count_vertices.c',
+  'nir_inline_sysval.c',
   'nir_inline_uniforms.c',
   'nir_instr_set.c',
   'nir_instr_set.h',

src/compiler/nir/nir.h

@@ -4945,6 +4945,8 @@ void nir_add_inlinable_uniforms(const nir_src *cond, nir_loop_info *info,
                                 uint32_t *uni_offsets, uint8_t *num_offsets,
                                 unsigned max_num_bo, unsigned max_offset);
 
+bool nir_inline_sysval(nir_shader *shader, nir_intrinsic_op op, uint64_t imm);
+
 bool nir_propagate_invariant(nir_shader *shader, bool invariant_prim);
 
 void nir_lower_var_copy_instr(nir_intrinsic_instr *copy, nir_shader *shader);

src/compiler/nir/nir_inline_sysval.c

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2025 Valve Corporation
+ * SPDX-License-Identifier: MIT
+ */
+
+#include "nir_builder.h"
+
+struct ctx {
+   nir_intrinsic_op op;
+   uint64_t imm;
+};
+
+static bool
+pass(nir_builder *b, nir_intrinsic_instr *intr, void *data)
+{
+   struct ctx *ctx = data;
+   if (intr->intrinsic != ctx->op)
+      return false;
+
+   b->cursor = nir_before_instr(&intr->instr);
+   nir_def_replace(&intr->def, nir_imm_intN_t(b, ctx->imm, intr->def.bit_size));
+   return true;
+}
+
+bool
+nir_inline_sysval(nir_shader *shader, nir_intrinsic_op op, uint64_t imm)
+{
+   struct ctx ctx = { .op = op, .imm = imm };
+   return nir_shader_intrinsics_pass(shader, pass, nir_metadata_control_flow,
+                                     &ctx);
+}