nir: Don't set LOD=0 for compute shader that has derivative group

When using NV_compute_shader_derivatives to set a derivative group,
a compute shader supports texture with implicit LOD calculation, so
don't set an explicit LOD.

Note if the extension is used but the derivative group is not
specified, it will default to LOD=0 as before.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

diff --git a/src/compiler/nir/nir_lower_tex.c b/src/compiler/nir/nir_lower_tex.c
index eee1b31..54db7b7 100644 (file)
--- a/src/compiler/nir/nir_lower_tex.c
+++ b/src/compiler/nir/nir_lower_tex.c
@@ -1111,14 +1111,18 @@ nir_lower_tex_block(nir_block *block, nir_builder *b,
          continue;
       }
 
+      bool shader_supports_implicit_lod =
+         b->shader->info.stage == MESA_SHADER_FRAGMENT ||
+         (b->shader->info.stage == MESA_SHADER_COMPUTE &&
+          b->shader->info.cs.derivative_group != DERIVATIVE_GROUP_NONE);
+
       /* TXF, TXS and TXL require a LOD but not everything we implement using those
        * three opcodes provides one.  Provide a default LOD of 0.
        */
       if ((nir_tex_instr_src_index(tex, nir_tex_src_lod) == -1) &&
           (tex->op == nir_texop_txf || tex->op == nir_texop_txs ||
            tex->op == nir_texop_txl || tex->op == nir_texop_query_levels ||
-           (tex->op == nir_texop_tex &&
-            b->shader->info.stage != MESA_SHADER_FRAGMENT))) {
+           (tex->op == nir_texop_tex && !shader_supports_implicit_lod))) {
          b->cursor = nir_before_instr(&tex->instr);
          nir_tex_instr_add_src(tex, nir_tex_src_lod, nir_src_for_ssa(nir_imm_int(b, 0)));
          progress = true;