diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 726809f3a88..9b8d39d00bb 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -1952,7 +1952,9 @@ typedef struct nir_io_semantics {
    unsigned no_sysval_output : 1; /* whether this system value output has no
                                      effect due to current pipeline states */
    unsigned interp_explicit_strict : 1; /* preserve original vertex order */
-   unsigned _pad : 1;
+   unsigned per_primitive : 1; /* Per-primitive FS input (when FS is used with a mesh shader).
+                                  Note that per-primitive MS outputs are implied by
+                                  using a dedicated intrinsic, store_per_primitive_output. */
 } nir_io_semantics;
 
 /* Transform feedback info for 2 outputs. nir_intrinsic_store_output contains
diff --git a/src/compiler/nir/nir_gather_info.c b/src/compiler/nir/nir_gather_info.c
index fc885c4d3a8..47e3a035f95 100644
--- a/src/compiler/nir/nir_gather_info.c
+++ b/src/compiler/nir/nir_gather_info.c
@@ -534,6 +534,8 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader,
          shader->info.inputs_read |= slot_mask;
          if (nir_intrinsic_io_semantics(instr).high_dvec2)
             shader->info.dual_slot_inputs |= slot_mask;
+         if (nir_intrinsic_io_semantics(instr).per_primitive)
+            shader->info.per_primitive_inputs |= slot_mask;
          shader->info.inputs_read_16bit |= slot_mask_16bit;
          if (!nir_src_is_const(*nir_get_io_offset_src(instr))) {
             shader->info.inputs_read_indirectly |= slot_mask;
diff --git a/src/compiler/nir/nir_intrinsics_indices_h.py b/src/compiler/nir/nir_intrinsics_indices_h.py
index 71bf5526ebd..9d5dbb30025 100644
--- a/src/compiler/nir/nir_intrinsics_indices_h.py
+++ b/src/compiler/nir/nir_intrinsics_indices_h.py
@@ -54,9 +54,6 @@ nir_intrinsic_set_${name}(nir_intrinsic_instr *instr, ${data_type} val)
    const nir_intrinsic_info *info = &nir_intrinsic_infos[instr->intrinsic];
    assert(info->index_map[${enum}] > 0);
 % if "struct" in data_type:
-% if name == "io_semantics":
-   val._pad = 0; /* clear padding bits */
-% endif
    STATIC_ASSERT(sizeof(instr->const_index[0]) == sizeof(val));
    memcpy(&instr->const_index[info->index_map[${enum}] - 1], &val, sizeof(val));
 % else:
diff --git a/src/compiler/nir/nir_lower_io.c b/src/compiler/nir/nir_lower_io.c
index d0e238b67b6..bb6ff15bd80 100644
--- a/src/compiler/nir/nir_lower_io.c
+++ b/src/compiler/nir/nir_lower_io.c
@@ -340,6 +340,7 @@ emit_load(struct lower_io_state *state,
          var->data.precision == GLSL_PRECISION_MEDIUM ||
          var->data.precision == GLSL_PRECISION_LOW;
       semantics.high_dvec2 = high_dvec2;
+      semantics.per_primitive = var->data.per_primitive;
       /* "per_vertex" is misnamed. It means "explicit interpolation with
        * the original vertex order", which is a stricter version of
        * INTERP_MODE_EXPLICIT.