nak: Move imad late optimization to nir

It is more or less just a code move, but I touched
is_only_used_by_iadd(..) to match the style of the other functions in
that file.

Signed-off-by: Christian Gmeiner <cgmeiner@igalia.com>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30099>

src/compiler/nir/nir_opt_algebraic.py

@@ -3143,7 +3143,10 @@ late_optimizations = [
 
    # nir_lower_to_source_mods will collapse this, but its existence during the
    # optimization loop can prevent other optimizations.
-   (('fneg', ('fneg', a)), a)
+   (('fneg', ('fneg', a)), a),
+
+   # combine imul and iadd to imad
+   (('iadd@32', ('imul(is_only_used_by_iadd)', a, b), c), ('imad', a, b, c), 'options->has_imad32'),
 ]
 
 # re-combine inexact mul+add to ffma. Do this before fsub so that a * b - c

src/compiler/nir/nir_search_helpers.h

@@ -583,6 +583,24 @@ is_only_used_by_fadd(const nir_alu_instr *instr)
    return true;
 }
 
+static inline bool
+is_only_used_by_iadd(const nir_alu_instr *instr)
+{
+   nir_foreach_use(src, &instr->def) {
+      const nir_instr *const user_instr = nir_src_parent_instr(src);
+      if (user_instr->type != nir_instr_type_alu)
+         return false;
+
+      const nir_alu_instr *const user_alu = nir_instr_as_alu(user_instr);
+      assert(instr != user_alu);
+
+      if (user_alu->op != nir_op_iadd)
+         return false;
+   }
+
+   return true;
+}
+
 static inline bool
 only_lower_8_bits_used(const nir_alu_instr *instr)
 {

src/nouveau/compiler/nak_nir_algebraic.py

@@ -39,11 +39,6 @@ algebraic_lowering = [
     (('umax', 'a', 'b'), ('bcsel', ('ult', a, b), b, a), volta),
 ]
 
-late_optimizations = [
-    (('iadd@32', ('imul(nak_is_only_used_by_iadd)', a, b), c),
-     ('imad', a, b, c), 'nak->sm >= 70'),
-]
-
 def main():
     parser = argparse.ArgumentParser()
     parser.add_argument('--out', required=True, help='Output file.')
@@ -58,7 +53,7 @@ def main():
             f.write('#include "nak_private.h"')
             f.write(nir_algebraic.AlgebraicPass(
                 "nak_nir_lower_algebraic_late",
-                algebraic_lowering + late_optimizations,
+                algebraic_lowering,
                 [
                     ("const struct nak_compiler *", "nak"),
                 ]).render())

src/nouveau/compiler/nak_private.h

@@ -222,21 +222,6 @@ bool nak_nir_lower_non_uniform_ldcx(nir_shader *nir);
 bool nak_nir_add_barriers(nir_shader *nir, const struct nak_compiler *nak);
 bool nak_nir_lower_cf(nir_shader *nir);
 
-static inline bool
-nak_is_only_used_by_iadd(const nir_alu_instr *instr)
-{
-   nir_foreach_use(src, &instr->def) {
-      nir_instr *use = nir_src_parent_instr(src);
-      if (use->type != nir_instr_type_alu)
-         return false;
-
-      if (nir_instr_as_alu(use)->op != nir_op_iadd)
-         return false;
-   }
-
-   return true;
-}
-
 void nak_optimize_nir(nir_shader *nir, const struct nak_compiler *nak);
 
 struct nak_memstream {