Mesa (main): zink: fix variable locations in manual xfb emission

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Module: Mesa
Branch: main
Commit: e9d28cbe3fbe56076f85e9e309211d831368d1fc
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=e9d28cbe3fbe56076f85e9e309211d831368d1fc

Author: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Date:   Sat May 21 18:53:59 2022 -0400

zink: fix variable locations in manual xfb emission

the last output isn't always only consuming 1 slot, so ensure that the
xfb outputs begin at the appropriate place

cc: mesa-stable

Reviewed-by: Adam Jackson <ajax at redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16669>

---

 src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c b/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
index f55cbff47af..18521103f10 100644
--- a/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
+++ b/src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c
@@ -4177,18 +4177,19 @@ nir_to_spirv(struct nir_shader *s, const struct zink_shader_info *sinfo, uint32_
    nir_foreach_shader_in_variable(var, s)
       emit_input(&ctx, var);
 
-   int max_output = -1;
+   int max_output = 0;
    nir_foreach_shader_out_variable(var, s) {
       /* ignore SPIR-V built-ins, tagged with a sentinel value */
       if (var->data.driver_location != UINT_MAX) {
          assert(var->data.driver_location < INT_MAX);
-         max_output = MAX2(max_output, (int)var->data.driver_location);
+         unsigned extent = glsl_count_attribute_slots(var->type, false);
+         max_output = MAX2(max_output, (int)var->data.driver_location + extent);
       }
       emit_output(&ctx, var);
    }
 
    if (sinfo->last_vertex)
-      emit_so_info(&ctx, sinfo, max_output + 1);
+      emit_so_info(&ctx, sinfo, max_output);
    uint32_t tcs_vertices_out_word = 0;
 
    /* we have to reverse iterate to match what's done in zink_compiler.c */