nir,amd: add nir_intrinsic_load_debug_log_desc_amd and its use

for shader debugging

Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27952>

src/amd/common/ac_nir.c

@@ -1259,3 +1259,26 @@ ac_nir_lower_legacy_gs(nir_shader *nir,
    if (progress)
       nir_metadata_preserve(impl, nir_metadata_none);
 }
+
+/* Shader logging function for printing nir_def values. The driver prints this after
+ * command submission.
+ *
+ * Ring buffer layout: {uint32_t num_dwords; vec4; vec4; vec4; ... }
+ * - The buffer size must be 2^N * 16 + 4
+ * - num_dwords is incremented atomically and the ring wraps around, removing
+ *   the oldest entries.
+ */
+void
+ac_nir_store_debug_log_amd(nir_builder *b, nir_def *uvec4)
+{
+   nir_def *buf = nir_load_debug_log_desc_amd(b);
+   nir_def *zero = nir_imm_int(b, 0);
+
+   nir_def *max_index =
+      nir_iadd_imm(b, nir_ushr_imm(b, nir_iadd_imm(b, nir_channel(b, buf, 2), -4), 4), -1);
+   nir_def *index = nir_ssbo_atomic(b, 32, buf, zero, nir_imm_int(b, 1),
+                                    .atomic_op = nir_atomic_op_iadd);
+   index = nir_iand(b, index, max_index);
+   nir_def *offset = nir_iadd_imm(b, nir_imul_imm(b, index, 16), 4);
+   nir_store_buffer_amd(b, uvec4, buf, offset, zero, zero);
+}

src/amd/common/ac_nir.h

@@ -352,6 +352,9 @@ typedef struct {
 bool
 ac_nir_lower_tex(nir_shader *nir, const ac_nir_lower_tex_options *options);
 
+void
+ac_nir_store_debug_log_amd(nir_builder *b, nir_def *uvec4);
+
 #ifdef __cplusplus
 }
 #endif

src/compiler/nir/nir_divergence_analysis.c

@@ -229,6 +229,7 @@ visit_intrinsic(nir_intrinsic_instr *instr, struct divergence_state *state)
    case nir_intrinsic_load_poly_line_smooth_enabled:
    case nir_intrinsic_load_rasterization_primitive_amd:
    case nir_intrinsic_load_global_constant_uniform_block_intel:
+   case nir_intrinsic_load_debug_log_desc_amd:
    case nir_intrinsic_cmat_length:
       is_divergent = false;
       break;

src/compiler/nir/nir_intrinsics.py

@@ -1737,6 +1737,9 @@ intrinsic("strict_wqm_coord_amd", src_comp=[0], dest_comp=0, bit_sizes=[32], ind
 intrinsic("cmat_muladd_amd", src_comp=[16, 16, 0], dest_comp=0, bit_sizes=src2,
           indices=[SATURATE, CMAT_SIGNED_MASK], flags=[CAN_ELIMINATE])
 
+# Get the debug log buffer descriptor.
+intrinsic("load_debug_log_desc_amd", bit_sizes=[32], dest_comp=4, flags=[CAN_ELIMINATE, CAN_REORDER])
+
 # V3D-specific instrinc for tile buffer color reads.
 #
 # The hardware requires that we read the samples and components of a pixel