Mesa (main): nir_to_tgsi: Support integer sysvals on !CAP_INTEGERS hardware.

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Module: Mesa
Branch: main
Commit: 026452fe466f2537ce2496efd008b16d1be5053b
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=026452fe466f2537ce2496efd008b16d1be5053b

Author: Emma Anholt <emma at anholt.net>
Date:   Sun Jun 13 08:07:14 2021 -0700

nir_to_tgsi: Support integer sysvals on !CAP_INTEGERS hardware.

glsl_to_tgsi does the same thing, needed for the draw path on i915g.

Reviewed-by: Adam Jackson <ajax at redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11329>

---

 src/gallium/auxiliary/nir/nir_to_tgsi.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/gallium/auxiliary/nir/nir_to_tgsi.c b/src/gallium/auxiliary/nir/nir_to_tgsi.c
index 1da966277b0..475243bf2cb 100644
--- a/src/gallium/auxiliary/nir/nir_to_tgsi.c
+++ b/src/gallium/auxiliary/nir/nir_to_tgsi.c
@@ -1640,6 +1640,23 @@ ntt_emit_load_sysval(struct ntt_compile *c, nir_intrinsic_instr *instr)
    uint32_t write_mask = BITSET_MASK(nir_dest_num_components(instr->dest));
    sv = ntt_swizzle_for_write_mask(sv, write_mask);
 
+   /* TGSI and NIR define these intrinsics as always loading ints, but they can
+    * still appear on hardware with non-native-integers fragment shaders using
+    * the draw path (i915g).  In that case, having called nir_lower_int_to_float
+    * means that we actually want floats instead.
+    */
+   if (!c->native_integers) {
+      switch (instr->intrinsic) {
+      case nir_intrinsic_load_vertex_id:
+      case nir_intrinsic_load_instance_id:
+         ureg_U2F(c->ureg, ntt_get_dest(c, &instr->dest), sv);
+         return;
+
+      default:
+         break;
+      }
+   }
+
    ntt_store(c, &instr->dest, sv);
 }