nir: plumb load_global_bounded

this lets the backend implement bounded loads (i.e. robust SSBOs) in a way
that's more clever than a full branch. similar idea to
load_global_constant_bound which should eventually be merged into this.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Job Noorman <job@noorman.info>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35720>

src/compiler/nir/nir_divergence_analysis.c

@@ -716,6 +716,7 @@ visit_intrinsic(nir_intrinsic_instr *instr, struct divergence_state *state)
    case nir_intrinsic_image_load_raw_intel:
    case nir_intrinsic_get_ubo_size:
    case nir_intrinsic_load_ssbo_address:
+   case nir_intrinsic_load_global_bounded:
    case nir_intrinsic_load_global_constant_bounded:
    case nir_intrinsic_load_global_constant_offset:
    case nir_intrinsic_load_reg:

src/compiler/nir/nir_intrinsics.py

@@ -1239,6 +1239,9 @@ load("constant", [1], [BASE, RANGE, ACCESS, ALIGN_MUL, ALIGN_OFFSET],
      [CAN_ELIMINATE, CAN_REORDER])
 # src[] = { address }.
 load("global", [1], [ACCESS, ALIGN_MUL, ALIGN_OFFSET], [CAN_ELIMINATE])
+# src[] = { base_address, offset, bound }.
+load("global_bounded", [1, 1, 1], [ACCESS, ALIGN_MUL, ALIGN_OFFSET],
+     [CAN_ELIMINATE])
 # src[] = { address }.
 load("global_2x32", [2], [ACCESS, ALIGN_MUL, ALIGN_OFFSET], [CAN_ELIMINATE])
 # src[] = { address }.

src/compiler/nir/nir_lower_io.c

@@ -1525,7 +1525,10 @@ build_explicit_io_load(nir_builder *b, nir_intrinsic_instr *intrin,
             op = nir_intrinsic_load_ubo;
          break;
       case nir_var_mem_ssbo:
-         if (addr_format_is_global(addr_format, mode))
+         if (addr_format == nir_address_format_64bit_bounded_global &&
+             b->shader->options->has_load_global_bounded)
+            op = nir_intrinsic_load_global_bounded;
+         else if (addr_format_is_global(addr_format, mode))
             op = nir_intrinsic_load_global;
          else
             op = nir_intrinsic_load_ssbo;
@@ -1608,7 +1611,8 @@ build_explicit_io_load(nir_builder *b, nir_intrinsic_instr *intrin,
       load->src[0] = nir_src_for_ssa(
          nir_pack_64_2x32(b, nir_trim_vector(b, addr, 2)));
       load->src[1] = nir_src_for_ssa(nir_channel(b, addr, 3));
-   } else if (op == nir_intrinsic_load_global_constant_bounded) {
+   } else if (op == nir_intrinsic_load_global_bounded ||
+              op == nir_intrinsic_load_global_constant_bounded) {
       assert(addr_format == nir_address_format_64bit_bounded_global);
       load->src[0] = nir_src_for_ssa(
          nir_pack_64_2x32(b, nir_trim_vector(b, addr, 2)));
@@ -1665,8 +1669,9 @@ build_explicit_io_load(nir_builder *b, nir_intrinsic_instr *intrin,
 
    nir_def *result;
    if (addr_format_needs_bounds_check(addr_format) &&
-       op != nir_intrinsic_load_global_constant_bounded) {
-      /* We don't need to bounds-check global_constant_bounded because bounds
+       op != nir_intrinsic_load_global_constant_bounded &&
+       op != nir_intrinsic_load_global_bounded) {
+      /* We don't need to bounds-check global_(constant_)bounded because bounds
        * checking is handled by the intrinsic itself.
        *
        * The Vulkan spec for robustBufferAccess gives us quite a few options
@@ -2079,7 +2084,7 @@ nir_lower_explicit_io_instr(nir_builder *b,
     * is to just split any loads and stores into individual components here.
     *
     * TODO: At some point in the future we may want to add more ops similar to
-    * nir_intrinsic_load_global_constant_bounded and make bouds checking the
+    * nir_intrinsic_load_global_(constant_)bounded and make bouds checking the
     * back-end's problem.  Another option would be to somehow plumb more of
     * that information through to nir_lower_explicit_io.  For now, however,
     * scalarizing is at least correct.

src/compiler/nir/nir_opt_preamble.c

@@ -246,6 +246,7 @@ can_move_intrinsic(nir_intrinsic_instr *instr, opt_preamble_ctx *ctx)
    case nir_intrinsic_image_load:
    case nir_intrinsic_image_samples_identical:
    case nir_intrinsic_bindless_image_load:
+   case nir_intrinsic_load_global_bounded:
    case nir_intrinsic_load_ssbo:
    case nir_intrinsic_load_ssbo_intel:
    case nir_intrinsic_load_ssbo_ir3:

src/compiler/nir/nir_opt_sink.c

@@ -119,6 +119,8 @@ can_sink_instr(nir_instr *instr, nir_move_options options, bool *can_mov_out_of_
       case nir_intrinsic_load_ssbo_intel:
          *can_mov_out_of_loop = false;
          return (options & nir_move_load_ssbo) && nir_intrinsic_can_reorder(intrin);
+      case nir_intrinsic_load_global_bounded:
+         return (options & nir_move_load_ssbo) && nir_intrinsic_can_reorder(intrin);
       case nir_intrinsic_load_input:
       case nir_intrinsic_load_per_primitive_input:
       case nir_intrinsic_load_interpolated_input:

src/compiler/nir/nir_shader_compiler_options.h

@@ -641,6 +641,9 @@ typedef struct nir_shader_compiler_options {
    /** Backend supports f2e4m3fn_satfn */
    bool has_f2e4m3fn_satfn;
 
+   /** Backend supports load_global_bounded intrinsics. */
+   bool has_load_global_bounded;
+
    /**
     * Is this the Intel vec4 backend?
     *