nir/print: Pretty-print I/O semantic locations

Instead of printing the raw location number, which is pretty hard to interpret,
let's print the name of the location. Example output:

   vec4 16 ssa_2 = intrinsic load_interpolated_input (ssa_0, ssa_1) (base=0,
   component=0, dest_type=float16 /*144*/, io location=VARYING_SLOT_VAR0 slots=1
   mediump /*8388768*/)

One of the "regressions" from moving to purely lowered I/O with all variables
removed is a lack of debuggability, since otherwise these location strings don't
show up anywhere in the printed shader! By contrast this should make the lowered
I/O nice to read like the early I/O.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Acked-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21091>

diff --git a/src/compiler/nir/nir_print.c b/src/compiler/nir/nir_print.c
index 01b8932..c898110 100644 (file)
--- a/src/compiler/nir/nir_print.c
+++ b/src/compiler/nir/nir_print.c
@@ -1053,7 +1053,33 @@ print_intrinsic_instr(nir_intrinsic_instr *instr, print_state *state)
 
       case NIR_INTRINSIC_IO_SEMANTICS: {
          struct nir_io_semantics io = nir_intrinsic_io_semantics(instr);
-         fprintf(fp, "io location=%u slots=%u", io.location, io.num_slots);
+
+         /* Try to figure out the mode so we can interpret the location */
+         nir_variable_mode mode = nir_var_mem_generic;
+         switch (instr->intrinsic) {
+         case nir_intrinsic_load_input:
+         case nir_intrinsic_load_interpolated_input:
+            mode = nir_var_shader_in;
+            break;
+
+         case nir_intrinsic_load_output:
+         case nir_intrinsic_store_output:
+         case nir_intrinsic_store_per_primitive_output:
+         case nir_intrinsic_store_per_vertex_output:
+            mode = nir_var_shader_out;
+            break;
+
+         default:
+            break;
+         }
+
+         /* Using that mode, we should be able to name the location */
+         char buf[4];
+         const char *loc = get_location_str(io.location,
+                                            state->shader->info.stage, mode,
+                                            buf);
+
+         fprintf(fp, "io location=%s slots=%u", loc, io.num_slots);
 
          if (io.dual_source_blend_index)
             fprintf(fp, " dualsrc");