Mesa (19.0): intel/nir: Vectorize all IO

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Module: Mesa
Branch: 19.0
Commit: 8d43691b269f94f88e469ff5eb15fa9e00be47c6
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=8d43691b269f94f88e469ff5eb15fa9e00be47c6

Author: Jason Ekstrand <jason.ekstrand at intel.com>
Date:   Thu Mar  7 15:01:37 2019 -0600

intel/nir: Vectorize all IO

The IO scalarization pass that we run to help with linking end up
turning some shader I/O such as that for tessellation and geometry
shaders into many scalar URB operations rather than one vector one.  To
alleviate this, we now vectorize the I/O once again.  This fixes a 10%
performance regression in the GfxBench tessellation test that was caused
by scalarizing.

Shader-db results on Kaby Lake:

    total instructions in shared programs: 15224023 -> 15220871 (-0.02%)
    instructions in affected programs: 342009 -> 338857 (-0.92%)
    helped: 1236
    HURT: 443

    total spills in shared programs: 23471 -> 23465 (-0.03%)
    spills in affected programs: 6 -> 0
    helped: 1
    HURT: 0

    total fills in shared programs: 31770 -> 31766 (-0.01%)
    fills in affected programs: 4 -> 0
    helped: 1
    HURT: 0

Cycles was just a lot of churn do to moves being different places.  Most
of the pure churn in instructions was +/- one or two instructions in
fragment shaders.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107510
Fixes: 4434591bf56a "intel/nir: Call nir_lower_io_to_scalar_early"
Fixes: 8d8222461f9d "intel/nir: Enable nir_opt_find_array_copies"
Reviewed-by: Connor Abbott <cwabbott0 at gmail.com>
(cherry picked from commit 6d5d89d25a0a4299dbfcbfeca71b6c7e65ef3d45)

---

 src/intel/compiler/brw_nir.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/src/intel/compiler/brw_nir.c b/src/intel/compiler/brw_nir.c
index bc1e2a5ef53..bc3abef709a 100644
--- a/src/intel/compiler/brw_nir.c
+++ b/src/intel/compiler/brw_nir.c
@@ -829,6 +829,23 @@ brw_nir_link_shaders(const struct brw_compiler *compiler,
       *producer = brw_nir_optimize(*producer, compiler, p_is_scalar, false);
       *consumer = brw_nir_optimize(*consumer, compiler, c_is_scalar, false);
    }
+
+   NIR_PASS_V(*producer, nir_lower_io_to_vector, nir_var_shader_out);
+   NIR_PASS_V(*consumer, nir_lower_io_to_vector, nir_var_shader_in);
+
+   if ((*producer)->info.stage != MESA_SHADER_TESS_CTRL) {
+      /* Calling lower_io_to_vector creates output variable writes with
+       * write-masks.  On non-TCS outputs, the back-end can't handle it and we
+       * need to call nir_lower_io_to_temporaries to get rid of them.  This,
+       * in turn, creates temporary variables and extra copy_deref intrinsics
+       * that we need to clean up.
+       */
+      NIR_PASS_V(*producer, nir_lower_io_to_temporaries,
+                 nir_shader_get_entrypoint(*producer), true, false);
+      NIR_PASS_V(*producer, nir_lower_global_vars_to_local);
+      NIR_PASS_V(*producer, nir_split_var_copies);
+      NIR_PASS_V(*producer, nir_lower_var_copies);
+   }
 }
 
 /* Prepare the given shader for codegen