panvk: Map ro_sink_address_poly to an OOB address

Mali hardware handles a bunch of OOB conditions by using addresses with
the top bit set.  When the top bit is set, any load/store from a shader
will treat the address as OOB and read zero and discard writes.  We can
use this to implement ro_sink_address_poly.

Signed-off-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38547>

src/panfrost/clc/pan_compile.c

@@ -194,6 +194,13 @@ lower_sysvals(nir_builder *b, nir_intrinsic_instr *intr, UNUSED void *_data)
          bit_size, num_comps);
       break;
 
+   case nir_intrinsic_load_ro_sink_address_poly:
+      /* Any address with the top bit set is treated as OOB by the hardware
+       * and any reads return zero.
+       */
+      val = nir_imm_int64(b, PAN_SHADER_OOB_ADDRESS);
+      break;
+
    case nir_intrinsic_load_printf_buffer_address:
       val = load_sysval_from_push_const(
          b,

src/panfrost/compiler/pan_compiler.h

@@ -28,6 +28,13 @@ void pan_postprocess_nir(nir_shader *nir, unsigned gpu_id);
 
 #define PAN_PRINTF_BUFFER_SIZE 16384
 
+/* Any address with the top bit set is treated OOB by the hardware when
+ * accessed from a shader and any reads will return zero and writes will be
+ * discarded.  Using these is sometimes preferable to control-flow in the
+ * shader.
+ */
+#define PAN_SHADER_OOB_ADDRESS (((uint64_t)1) << 63)
+
 /* Indices for named (non-XFB) varyings that are present. These are packed
  * tightly so they correspond to a bitfield present (P) indexed by (1 <<
  * PAN_VARY_*). This has the nice property that you can lookup the buffer index

src/panfrost/vulkan/panvk_vX_shader.c

@@ -181,6 +181,10 @@ panvk_lower_sysvals(nir_builder *b, nir_instr *instr, void *data)
       break;
    }
 
+   case nir_intrinsic_load_ro_sink_address_poly:
+      val = nir_imm_int64(b, PAN_SHADER_OOB_ADDRESS);
+      break;
+
    default:
       return false;
    }