Mesa (master): turnip: Offset by component when lowering gl_TessLevel*

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Module: Mesa
Branch: master
Commit: ff16e72545bdcf26ae02475d90f911d31518928e
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ff16e72545bdcf26ae02475d90f911d31518928e

Author: Brian Ho <brian at brkho.com>
Date:   Fri Apr 24 08:22:20 2020 -0700

turnip: Offset by component when lowering gl_TessLevel*

lower_tess_ctrl_block assumes that the gl_TessLevel*
intrinsic_store_outputs have already been collapsed into a single
instruction before the tess lowering step:

store_output ... /* base=0 */ /* wrmask=xyzw */ /* component=0 */
store_output ... /* base=1 */ /* wrmask=xy */ /* component=0 */

While this is true in fd because of st_nir_vectorize_io, we don't do
the same lowering in turnip so each tess level component still has
its own store instruction:

store_output ... /* base=0 */ /* wrmask=x */ /* component=0 */
store_output ... /* base=0 */ /* wrmask=x */ /* component=1 */
store_output ... /* base=0 */ /* wrmask=x */ /* component=2 */
store_output ... /* base=0 */ /* wrmask=x */ /* component=3 */
store_output ... /* base=1 */ /* wrmask=x */ /* component=0 */
store_output ... /* base=1 */ /* wrmask=x */ /* component=1 */

This commit adds a component offset to the tess control lowering. An
alternative is to also perform nir_lower_io_to_vector in turnip, but
ir3 seems to generate the same assembly either way and it's nice to
not have a lowering prereq before tess lowering.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5059>

---

 src/freedreno/ir3/ir3_nir_lower_tess.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/freedreno/ir3/ir3_nir_lower_tess.c b/src/freedreno/ir3/ir3_nir_lower_tess.c
index 458b29848a0..bdb98f3d935 100644
--- a/src/freedreno/ir3/ir3_nir_lower_tess.c
+++ b/src/freedreno/ir3/ir3_nir_lower_tess.c
@@ -503,9 +503,12 @@ lower_tess_ctrl_block(nir_block *block, nir_builder *b, struct state *state)
 			b->cursor = nir_before_instr(&intr->instr);
 
 			if (levels) {
-				for (int i = 0; i < 4; i++)
-					if (nir_intrinsic_write_mask(intr) & (1 << i))
-						levels[i] = nir_channel(b, intr->src[0].ssa, i);
+				for (int i = 0; i < 4; i++) {
+					if (nir_intrinsic_write_mask(intr) & (1 << i)) {
+						uint32_t component = nir_intrinsic_component(intr);
+						levels[i + component] = nir_channel(b, intr->src[0].ssa, i);
+					}
+				}
 				nir_instr_remove(&intr->instr);
 			} else {
 				nir_ssa_def *address = nir_load_tess_param_base_ir3(b);