Mesa (master): zink: put those shader keys to work fixing up fragment shaders

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Module: Mesa
Branch: master
Commit: eeff625ab31f0a1bf94739e09ca6b08de00c94f5
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=eeff625ab31f0a1bf94739e09ca6b08de00c94f5

Author: Mike Blumenkrantz <michael.blumenkrantz at gmail.com>
Date:   Mon Jul 13 17:37:10 2020 -0400

zink: put those shader keys to work fixing up fragment shaders

eliminate gl_SampleMask writes when necessary to mimic GL behavior

Reviewed-by: Erik Faye-Lund <erik.faye-lund at collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7193>

---

 src/gallium/drivers/zink/zink_compiler.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/gallium/drivers/zink/zink_compiler.c b/src/gallium/drivers/zink/zink_compiler.c
index dc3c829d01e..bdc08483cce 100644
--- a/src/gallium/drivers/zink/zink_compiler.c
+++ b/src/gallium/drivers/zink/zink_compiler.c
@@ -222,9 +222,26 @@ zink_shader_compile(struct zink_screen *screen, struct zink_shader *zs, struct z
 {
    VkShaderModule mod = VK_NULL_HANDLE;
    void *streamout = NULL;
+   nir_shader *nir = zs->nir;
+   /* TODO: use a separate mem ctx here for ralloc */
    if (zs->streamout.so_info_slots && (zs->nir->info.stage != MESA_SHADER_VERTEX || !zs->has_geometry_shader))
       streamout = &zs->streamout;
-   struct spirv_shader *spirv = nir_to_spirv(zs->nir, streamout, shader_slot_map, shader_slots_reserved);
+   if (zs->nir->info.stage == MESA_SHADER_FRAGMENT) {
+      nir = nir_shader_clone(NULL, nir);
+      if (!zink_fs_key(key)->samples && nir->info.outputs_written & BITFIELD64_BIT(FRAG_RESULT_SAMPLE_MASK)) {
+         /* VK will always use gl_SampleMask[] values even if sample count is 0,
+          * so we need to skip this write here to mimic GL's behavior of ignoring it
+          */
+         nir_foreach_shader_out_variable(var, nir) {
+            if (var->data.location == FRAG_RESULT_SAMPLE_MASK)
+               var->data.mode = nir_var_shader_temp;
+         }
+         nir_fixup_deref_modes(nir);
+         NIR_PASS_V(nir, nir_remove_dead_variables, nir_var_shader_temp, NULL);
+         optimize_nir(nir);
+      }
+   }
+   struct spirv_shader *spirv = nir_to_spirv(nir, streamout, shader_slot_map, shader_slots_reserved);
    assert(spirv);
 
    if (zink_debug & ZINK_DEBUG_SPIRV) {
@@ -247,6 +264,9 @@ zink_shader_compile(struct zink_screen *screen, struct zink_shader *zs, struct z
    if (vkCreateShaderModule(screen->dev, &smci, NULL, &mod) != VK_SUCCESS)
       mod = VK_NULL_HANDLE;
 
+   if (zs->nir->info.stage == MESA_SHADER_FRAGMENT)
+      ralloc_free(nir);
+
    /* TODO: determine if there's any reason to cache spirv output? */
    free(spirv->words);
    free(spirv);