intel/fs: Use shuffle_from_32bit_read at VARYING_PULL_CONSTANT_LOAD

shuffle_from_32bit_read can manage the shuffle/unshuffle needed
for different 8/16/32/64 bit-sizes at VARYING PULL CONSTANT LOAD.
To get the specific component the first_component parameter is used.

In the case of the previous 16-bit shuffle, the shuffle operation was
generating not needed MOVs where its results where never used. This
behaviour passed unnoticed on SIMD16 because dead_code_eliminate
pass removed the generated instructions but for SIMD8 they cound't be
removed because of being partial writes.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/compiler/brw_fs.cpp

@@ -191,21 +191,8 @@ fs_visitor::VARYING_PULL_CONSTANT_LOAD(const fs_builder &bld,
                             vec4_result, surf_index, vec4_offset);
    inst->size_written = 4 * vec4_result.component_size(inst->exec_size);
 
-   fs_reg dw = offset(vec4_result, bld, (const_offset & 0xf) / 4);
+   shuffle_from_32bit_read(bld, dst, vec4_result,
-   switch (type_sz(dst.type)) {
+                           (const_offset & 0xf) / type_sz(dst.type), 1);
-   case 2:
-      shuffle_32bit_load_result_to_16bit_data(bld, dst, dw, 0, 1);
-      bld.MOV(dst, subscript(dw, dst.type, (const_offset / 2) & 1));
-      break;
-   case 4:
-      bld.MOV(dst, retype(dw, dst.type));
-      break;
-   case 8:
-      shuffle_32bit_load_result_to_64bit_data(bld, dst, dw, 1);
-      break;
-   default:
-      unreachable("Unsupported bit_size");
-   }
 }
 
 /**