nir: Add nir_builder support for individual system value loads.

The previous nir_load_system_value(b, nir_intrinsic_load_whatever), 0) was
rather verbose, when system values should be easy to generate.

The index is left out because only one system value had an index included
in it.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/nir/nir_intrinsics.h

@@ -41,7 +41,6 @@
 
 #define ARR(...) { __VA_ARGS__ }
 
-
 INTRINSIC(load_var, 0, ARR(0), true, 0, 1, 0, xx, xx, xx, NIR_INTRINSIC_CAN_ELIMINATE)
 INTRINSIC(store_var, 1, ARR(0), false, 0, 1, 1, WRMASK, xx, xx, 0)
 INTRINSIC(copy_var, 0, ARR(0), false, 0, 2, 0, xx, xx, xx, 0)
@@ -277,7 +276,13 @@ INTRINSIC(shared_atomic_xor, 2, ARR(1, 1), true, 1, 0, 1, BASE, xx, xx, 0)
 INTRINSIC(shared_atomic_exchange, 2, ARR(1, 1), true, 1, 0, 1, BASE, xx, xx, 0)
 INTRINSIC(shared_atomic_comp_swap, 3, ARR(1, 1, 1), true, 1, 0, 1, BASE, xx, xx, 0)
 
+/* Used by nir_builder.h to generate loader helpers for the system values. */
+#ifndef DEFINE_SYSTEM_VALUE
+#define DEFINE_SYSTEM_VALUE(name)
+#endif
+
 #define SYSTEM_VALUE(name, components, num_indices, idx0, idx1, idx2) \
+   DEFINE_SYSTEM_VALUE(name) \
    INTRINSIC(load_##name, 0, ARR(0), true, components, 0, num_indices, \
    idx0, idx1, idx2, \
    NIR_INTRINSIC_CAN_ELIMINATE | NIR_INTRINSIC_CAN_REORDER)
@@ -406,5 +411,6 @@ STORE(shared, 2, 2, BASE, WRMASK, xx, 0)
 
 LAST_INTRINSIC(store_shared)
 
+#undef DEFINE_SYSTEM_VALUE
 #undef INTRINSIC
 #undef LAST_INTRINSIC