broadcom: drop backend implementation of nir_op_ufind_msb

We can have NIR do this for us now that we have uclz.

Suggested by Georg Lehmann.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30614>

src/broadcom/compiler/nir_to_vir.c

@@ -1619,10 +1619,6 @@ ntq_emit_alu(struct v3d_compile *c, nir_alu_instr *instr)
                 result = vir_CLZ(c, src[0]);
                 break;
 
-        case nir_op_ufind_msb:
-                result = vir_SUB(c, vir_uniform_ui(c, 31), vir_CLZ(c, src[0]));
-                break;
-
         case nir_op_imul:
                 result = vir_UMUL(c, src[0], src[1]);
                 break;

src/broadcom/vulkan/v3dv_pipeline.c

@@ -218,6 +218,7 @@ v3dv_pipeline_get_nir_options(const struct v3d_device_info *devinfo)
       .lower_to_scalar = true,
       .lower_device_index_to_zero = true,
       .lower_fquantize2f16 = true,
+      .lower_ufind_msb = true,
       .has_fsub = true,
       .has_isub = true,
       .has_uclz = true,

src/gallium/drivers/v3d/v3d_screen.c

@@ -749,6 +749,7 @@ v3d_screen_get_compiler_options(struct pipe_screen *pscreen,
                         nir_lower_shift64 |
                         nir_lower_ufind_msb64,
                 .lower_fquantize2f16 = true,
+                .lower_ufind_msb = true,
                 .has_fsub = true,
                 .has_isub = true,
                 .has_uclz = true,