nir: update fallthrough comments

clang doesn't support /* fallthrough */ so switch to fallthrough
attribute.

Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7747>

src/compiler/glsl/gl_nir_linker.c

@@ -288,7 +288,7 @@ add_shader_variable(const struct gl_context *ctx,
          return true;
       }
    }
-   /* fallthrough */
+   FALLTHROUGH;
 
    default: {
       /* The ARB_program_interface_query spec says:

src/compiler/nir/nir.c

@@ -1741,7 +1741,7 @@ nir_block_cf_tree_next(nir_block *block)
 
       assert(block == nir_if_last_else_block(if_stmt));
    }
-   /* fallthrough */
+   FALLTHROUGH;
 
    case nir_cf_node_loop:
       return nir_cf_node_as_block(nir_cf_node_next(parent));
@@ -1779,7 +1779,7 @@ nir_block_cf_tree_prev(nir_block *block)
 
       assert(block == nir_if_first_then_block(if_stmt));
    }
-   /* fallthrough */
+   FALLTHROUGH;
 
    case nir_cf_node_loop:
       return nir_cf_node_as_block(nir_cf_node_prev(parent));

src/compiler/nir/nir.h

@@ -36,6 +36,7 @@
 #include "util/set.h"
 #include "util/bitscan.h"
 #include "util/bitset.h"
+#include "util/compiler.h"
 #include "util/enum_operators.h"
 #include "util/macros.h"
 #include "util/format/u_format.h"

src/compiler/nir/nir_divergence_analysis.c

@@ -230,7 +230,7 @@ visit_intrinsic(nir_shader *shader, nir_intrinsic_instr *instr)
    case nir_intrinsic_reduce:
       if (nir_intrinsic_cluster_size(instr) == 0)
          return false;
-      /* fallthrough */
+      FALLTHROUGH;
    case nir_intrinsic_inclusive_scan: {
       nir_op op = nir_intrinsic_reduction_op(instr);
       is_divergent = instr->src[0].ssa->divergent;
@@ -567,7 +567,7 @@ visit_deref(nir_shader *shader, nir_deref_instr *deref)
    case nir_deref_type_array:
    case nir_deref_type_ptr_as_array:
       is_divergent = deref->arr.index.ssa->divergent;
-      /* fallthrough */
+      FALLTHROUGH;
    case nir_deref_type_struct:
    case nir_deref_type_array_wildcard:
       is_divergent |= deref->parent.ssa->divergent;

src/compiler/nir/nir_gather_info.c

@@ -328,6 +328,7 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader,
    case nir_intrinsic_demote:
    case nir_intrinsic_demote_if:
       shader->info.fs.uses_demote = true;
+      FALLTHROUGH;
    /* fallthrough - quads with helper lanes only might be discarded entirely */
    case nir_intrinsic_discard:
    case nir_intrinsic_discard_if:
@@ -445,7 +446,7 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader,
       shader->info.inputs_read |=
          BITFIELD64_BIT(VARYING_SLOT_COL0 <<
                         (instr->intrinsic == nir_intrinsic_load_color1));
-      /* fall through */
+      FALLTHROUGH;
    case nir_intrinsic_load_subgroup_size:
    case nir_intrinsic_load_subgroup_invocation:
    case nir_intrinsic_load_subgroup_eq_mask:
@@ -573,7 +574,7 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader,
    case nir_intrinsic_end_primitive_with_counter:
       assert(shader->info.stage == MESA_SHADER_GEOMETRY);
       shader->info.gs.uses_end_primitive = 1;
-      /* fall through */
+      FALLTHROUGH;
 
    case nir_intrinsic_emit_vertex:
    case nir_intrinsic_emit_vertex_with_counter:
@@ -737,7 +738,7 @@ gather_alu_info(nir_alu_instr *instr, nir_shader *shader)
    case nir_op_fddx:
    case nir_op_fddy:
       shader->info.uses_fddx_fddy = true;
-      /* Fall through */
+      FALLTHROUGH;
    case nir_op_fddx_fine:
    case nir_op_fddy_fine:
    case nir_op_fddx_coarse:

src/compiler/nir/nir_lower_bool_to_bitsize.c

@@ -111,7 +111,7 @@ lower_alu_instr(nir_builder *b, nir_alu_instr *alu)
    case nir_op_ixor:
       if (nir_dest_bit_size(alu->dest.dest) > 1)
          return false; /* Not a boolean instruction */
-      /* Fallthrough */
+      FALLTHROUGH;
 
    case nir_op_ball_fequal2:
    case nir_op_ball_fequal3:

src/compiler/nir/nir_lower_io.c

@@ -613,6 +613,7 @@ nir_lower_io_block(nir_block *block,
          if (options->use_interpolated_input_intrinsics ||
              options->lower_interpolate_at)
             break;
+         FALLTHROUGH;
       default:
          /* We can't lower the io for this nir instrinsic, so skip it */
          continue;

src/compiler/nir/nir_lower_phis_to_scalar.c

@@ -110,7 +110,7 @@ is_phi_src_scalarizable(nir_phi_src *src,
          break;
       }
    }
-   /* fallthrough */
+   FALLTHROUGH;
 
    default:
       /* We can't scalarize this type of instruction */

src/compiler/nir/nir_opt_gcm.c

@@ -207,7 +207,7 @@ gcm_pin_instructions(nir_function_impl *impl, struct gcm_state *state)
                   instr->pass_flags = GCM_INSTR_PINNED;
                   break;
                }
-               /* fallthrough */
+               FALLTHROUGH;
 
             default:
                instr->pass_flags = 0;

src/compiler/nir/nir_propagate_invariant.c

@@ -127,6 +127,7 @@ propagate_invariant_instr(nir_instr *instr, struct set *invariants)
          /* Nothing to do */
          break;
       }
+      FALLTHROUGH;
    }
 
    case nir_instr_type_deref:

src/compiler/nir/nir_range_analysis.c

@@ -864,6 +864,7 @@ analyze_expression(const nir_alu_instr *instr, unsigned src,
 
       case eq_zero:
          assert(r.is_integral);
+         FALLTHROUGH;
       case gt_zero:
       case ge_zero:
          /* The fsat doesn't add any information in these cases. */

src/compiler/nir/nir_split_vars.c

@@ -495,7 +495,7 @@ mark_array_usage_impl(nir_function_impl *impl,
          case nir_intrinsic_copy_deref:
             mark_array_deref_used(nir_src_as_deref(intrin->src[1]),
                                   var_info_map, modes, mem_ctx);
-            /* Fall Through */
+            FALLTHROUGH;
 
          case nir_intrinsic_load_deref:
          case nir_intrinsic_store_deref:

src/compiler/nir/nir_to_lcssa.c

@@ -179,7 +179,7 @@ instr_is_invariant(nir_instr *instr, nir_loop *loop)
       if (!(nir_intrinsic_infos[intrinsic->intrinsic].flags & NIR_INTRINSIC_CAN_REORDER))
          return not_invariant;
    }
-   /* fallthrough */
+   FALLTHROUGH;
    default:
       return nir_foreach_src(instr, src_is_invariant, loop) ? invariant : not_invariant;
    }

src/compiler/nir/nir_validate.c

@@ -644,7 +644,7 @@ validate_intrinsic_instr(nir_intrinsic_instr *instr, validate_state *state)
    case nir_intrinsic_load_ubo:
       /* Make sure that the creator didn't forget to set the range_base+range. */
       validate_assert(state, nir_intrinsic_range(instr) != 0);
-      /* Fall through */
+      FALLTHROUGH;
    case nir_intrinsic_load_ssbo:
    case nir_intrinsic_load_shared:
    case nir_intrinsic_load_global:
@@ -656,7 +656,7 @@ validate_intrinsic_instr(nir_intrinsic_instr *instr, validate_state *state)
          util_is_power_of_two_nonzero(nir_intrinsic_align_mul(instr)));
       validate_assert(state, nir_intrinsic_align_offset(instr) <
                              nir_intrinsic_align_mul(instr));
-      /* Fall through */
+      FALLTHROUGH;
 
    case nir_intrinsic_load_uniform:
    case nir_intrinsic_load_input:
@@ -678,7 +678,7 @@ validate_intrinsic_instr(nir_intrinsic_instr *instr, validate_state *state)
          util_is_power_of_two_nonzero(nir_intrinsic_align_mul(instr)));
       validate_assert(state, nir_intrinsic_align_offset(instr) <
                              nir_intrinsic_align_mul(instr));
-      /* Fall through */
+      FALLTHROUGH;
 
    case nir_intrinsic_store_output:
    case nir_intrinsic_store_per_vertex_output: