Mesa (master): mesa/st: glsl_to_nir: don't lower atomics to SSBOs if driver supports HW atomics

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Module: Mesa
Branch: master
Commit: 9162e2f03fba0308f889e74036c77b127fddeba5
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=9162e2f03fba0308f889e74036c77b127fddeba5

Author: Gert Wollny <gert.wollny at collabora.com>
Date:   Sat Dec 28 16:07:30 2019 +0100

mesa/st: glsl_to_nir: don't lower atomics to SSBOs if driver supports HW atomics

At least on r600 HW atomic operations are way less expensive than SSBO atomic
operations.

v2: use st->has_hw_atomics (Erik Anholt)

v3: remove second invocation of atomic to ssbo lowering (Erik Anholt)

Signed-off-by: Gert Wollny <gert.wollny at collabora.com>
Reviewed-by: Eric Anholt <eric at anholt.net>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3286>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3286>

---

 src/mesa/state_tracker/st_glsl_to_nir.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp b/src/mesa/state_tracker/st_glsl_to_nir.cpp
index 322143d1e7b..a277c0eef31 100644
--- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
@@ -504,8 +504,9 @@ st_glsl_to_nir_post_opts(struct st_context *st, struct gl_program *prog,
       (nir_var_shader_in | nir_var_shader_out | nir_var_function_temp );
    nir_remove_dead_variables(nir, mask);
 
-   NIR_PASS_V(nir, nir_lower_atomics_to_ssbo,
-              st->ctx->Const.Program[nir->info.stage].MaxAtomicBuffers);
+   if (!st->has_hw_atomics)
+      NIR_PASS_V(nir, nir_lower_atomics_to_ssbo,
+                 st->ctx->Const.Program[nir->info.stage].MaxAtomicBuffers);
 
    st_finalize_nir_before_variants(nir);