radv: run nir_opt_shrink_load

LLVM can't shrink loads.

Polaris10:
Totals from affected shaders:
SGPRS: 62528 -> 59955 (-4.11 %)
VGPRS: 44708 -> 44616 (-0.21 %)
Spilled SGPRs: 16 -> 8 (-50.00 %)
Code Size: 1355504 -> 1355172 (-0.02 %) bytes
Max Waves: 11710 -> 11670 (-0.34 %)

Vega10:
Totals from affected shaders:
SGPRS: 51448 -> 50371 (-2.09 %)
VGPRS: 39140 -> 39048 (-0.24 %)
Spilled SGPRs: 16 -> 16 (0.00 %)
Code Size: 1307188 -> 1304296 (-0.22 %) bytes
Max Waves: 11312 -> 11292 (-0.18 %)

This reduces SGPRs spilling in MadMax, and it also reduces
number of SGPRs in DOW3 and F12017. The number of waves slightly
decreases in F1 but I don't see any performance changes after
benchmarking it. Talos and Serious Sam are not affected because
they don't use any push constants.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>

src/amd/vulkan/radv_shader.c

@@ -148,6 +148,8 @@ radv_optimize_nir(struct nir_shader *shader)
                         NIR_PASS(progress, shader, nir_opt_loop_unroll, 0);
                 }
         } while (progress);
+
+        NIR_PASS(progress, shader, nir_opt_shrink_load);
 }
 
 nir_shader *