st/glsl: Perform some var optimizations

Perform those before some derefs are gone when we lower the buffers
after the st_nir_opts() call.

Intel SKL shader-db results:

    total instructions in shared programs: 15593685 -> 15590708 (-0.02%)
    instructions in affected programs: 378078 -> 375101 (-0.79%)
    helped: 777
    HURT: 44
    helped stats (abs) min: 1 max: 68 x̄: 4.07 x̃: 4
    helped stats (rel) min: 0.04% max: 31.58% x̄: 2.88% x̃: 1.37%
    HURT stats (abs)   min: 1 max: 24 x̄: 4.20 x̃: 2
    HURT stats (rel)   min: 0.17% max: 8.00% x̄: 1.60% x̃: 1.27%
    95% mean confidence interval for instructions value: -4.02 -3.23
    95% mean confidence interval for instructions %-change: -2.93% -2.35%
    Instructions are helped.

    total loops in shared programs: 4815 -> 4815 (0.00%)
    loops in affected programs: 0 -> 0
    helped: 0
    HURT: 0

    total cycles in shared programs: 371965528 -> 371788566 (-0.05%)
    cycles in affected programs: 184190307 -> 184013345 (-0.10%)
    helped: 3650
    HURT: 2855
    helped stats (abs) min: 1 max: 59400 x̄: 99.45 x̃: 15
    helped stats (rel) min: <.01% max: 43.18% x̄: 2.60% x̃: 1.02%
    HURT stats (abs)   min: 1 max: 16362 x̄: 65.16 x̃: 10
    HURT stats (rel)   min: <.01% max: 66.22% x̄: 2.78% x̃: 0.81%
    95% mean confidence interval for cycles value: -53.73 -0.68
    95% mean confidence interval for cycles %-change: -0.39% -0.08%
    Cycles are helped.

    total spills in shared programs: 11936 -> 11956 (0.17%)
    spills in affected programs: 443 -> 463 (4.51%)
    helped: 0
    HURT: 8

    total fills in shared programs: 25644 -> 25619 (-0.10%)
    fills in affected programs: 2306 -> 2281 (-1.08%)
    helped: 24
    HURT: 2

    LOST:   7
    GAINED: 16

    Total CPU time (seconds): 1679.04 -> 1695.69 (0.99%)

shader-db results radeonsi (VEGA64):

    Totals from affected shaders:
    SGPRS: 180160 -> 179552 (-0.34 %)
    VGPRS: 115368 -> 114544 (-0.71 %)
    Spilled SGPRs: 5627 -> 5603 (-0.43 %)
    Spilled VGPRs: 0 -> 0 (0.00 %)
    Private memory VGPRs: 0 -> 0 (0.00 %)
    Scratch size: 0 -> 0 (0.00 %) dwords per thread
    Code Size: 7808364 -> 7803268 (-0.07 %) bytes
    LDS: 192 -> 192 (0.00 %) blocks
    Max Waves: 19202 -> 19340 (0.72 %)
    Wait states: 0 -> 0 (0.00 %)

Radeonsi results provided by Timothy.

Reviewed-by: Timothy Arceri <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/mesa/state_tracker/st_glsl_to_nir.cpp b/src/mesa/state_tracker/st_glsl_to_nir.cpp
index b40cb9223df..e4303b0250c 100644
--- a/src/mesa/state_tracker/st_glsl_to_nir.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_nir.cpp
@@ -314,6 +314,9 @@ st_nir_opts(nir_shader *nir, bool scalar)
 
       NIR_PASS_V(nir, nir_lower_vars_to_ssa);
 
+      NIR_PASS(progress, nir, nir_opt_copy_prop_vars);
+      NIR_PASS(progress, nir, nir_opt_dead_write_vars);
+
       if (scalar) {
          NIR_PASS_V(nir, nir_lower_alu_to_scalar, NULL);
          NIR_PASS_V(nir, nir_lower_phis_to_scalar);