microsoft/compiler: Remove deref load/store/atomic ops that statically go out of array bounds

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27919>

src/microsoft/compiler/dxil_nir.c

@@ -608,6 +608,55 @@ dxil_nir_lower_var_bit_size(nir_shader *shader, nir_variable_mode modes,
    return true;
 }
 
+static bool
+remove_oob_array_access(nir_builder *b, nir_intrinsic_instr *intr, void *data)
+{
+   uint32_t num_derefs = 1;
+
+   switch (intr->intrinsic) {
+   case nir_intrinsic_copy_deref:
+      num_derefs = 2;
+      FALLTHROUGH;
+   case nir_intrinsic_load_deref:
+   case nir_intrinsic_store_deref:
+   case nir_intrinsic_deref_atomic:
+   case nir_intrinsic_deref_atomic_swap:
+      break;
+   default:
+      return false;
+   }
+
+   for (uint32_t i = 0; i < num_derefs; ++i) {
+      if (nir_deref_instr_is_known_out_of_bounds(nir_src_as_deref(intr->src[i]))) {
+         switch (intr->intrinsic) {
+         case nir_intrinsic_load_deref:
+         case nir_intrinsic_deref_atomic:
+         case nir_intrinsic_deref_atomic_swap:
+            b->cursor = nir_before_instr(&intr->instr);
+            nir_def *undef = nir_undef(b, intr->def.num_components, intr->def.bit_size);
+            nir_def_rewrite_uses(&intr->def, undef);
+            break;
+         default:
+            break;
+         }
+         nir_instr_remove(&intr->instr);
+         return true;
+      }
+   }
+
+   return false;
+}
+
+bool
+dxil_nir_remove_oob_array_accesses(nir_shader *shader)
+{
+   return nir_shader_intrinsics_pass(shader, remove_oob_array_access,
+                                     nir_metadata_block_index |
+                                        nir_metadata_dominance |
+                                        nir_metadata_loop_analysis,
+                                     NULL);
+}
+
 static bool
 lower_shared_atomic(nir_builder *b, nir_intrinsic_instr *intr, nir_variable *var)
 {

src/microsoft/compiler/dxil_nir.h

@@ -40,6 +40,7 @@ bool dxil_nir_lower_constant_to_temp(nir_shader *shader);
 bool dxil_nir_flatten_var_arrays(nir_shader *shader, nir_variable_mode modes);
 bool dxil_nir_lower_var_bit_size(nir_shader *shader, nir_variable_mode modes,
                                  unsigned min_bit_size, unsigned max_bit_size);
+bool dxil_nir_remove_oob_array_accesses(nir_shader *shader);
 struct dxil_nir_lower_loads_stores_options {
    bool use_16bit_ssbo;
 };

src/microsoft/compiler/nir_to_dxil.c

@@ -6331,6 +6331,7 @@ optimize_nir(struct nir_shader *s, const struct nir_to_dxil_options *opts)
       NIR_PASS(progress, s, nir_lower_phis_to_scalar, true);
       NIR_PASS(progress, s, nir_opt_loop_unroll);
       NIR_PASS(progress, s, nir_lower_pack);
+      NIR_PASS(progress, s, dxil_nir_remove_oob_array_accesses);
       NIR_PASS_V(s, nir_lower_system_values);
    } while (progress);