i965/gs: Do prog_data setup and other calculations in brw_compile_gs

This commit moves the large pile of setup calculations we have to do for
geometry shaders out of brw_gs_emit and into brw_compile_gs.  This has a
couple of nice implications.  First, it's less work that the caller of
brw_compile_gs has to do.  Second, it's consistent with the vertex and
fragment stages.  Finally, it allows us to put brw_gs_compile back behind
the API boundary where it belongs.

v2 (Jason Ekstrand):
 - Pull the changes to use nir info into a separate patch
 - Put brw_gs_compile into brw_shader.h rather than brw_vec4_gs_visitor.h
   so that we can use it for scalar GS.

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

1 files changed, 207 insertions, 4 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
index faad1a8..9402489 100644
--- a/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_vec4_gs_visitor.cpp
@@ -601,7 +601,7 @@ vec4_gs_visitor::gs_end_primitive()
 extern "C" const unsigned *
 brw_compile_gs(const struct brw_compiler *compiler, void *log_data,
                void *mem_ctx,
-               struct brw_gs_compile *c,
+               const struct brw_gs_prog_key *key,
                struct brw_gs_prog_data *prog_data,
                const nir_shader *shader,
                struct gl_shader_program *shader_prog,
@@ -609,6 +609,209 @@ brw_compile_gs(const struct brw_compiler *compiler, void *log_data,
                unsigned *final_assembly_size,
                char **error_str)
 {
+   struct brw_gs_compile c;
+   memset(&c, 0, sizeof(c));
+   c.key = *key;
+
+   prog_data->include_primitive_id =
+      (shader->info.inputs_read & VARYING_BIT_PRIMITIVE_ID) != 0;
+
+   prog_data->invocations = shader->info.gs.invocations;
+
+   if (compiler->devinfo->gen >= 8)
+      prog_data->static_vertex_count = nir_gs_count_vertices(shader);
+
+   if (compiler->devinfo->gen >= 7) {
+      if (shader->info.gs.output_primitive == GL_POINTS) {
+         /* When the output type is points, the geometry shader may output data
+          * to multiple streams, and EndPrimitive() has no effect.  So we
+          * configure the hardware to interpret the control data as stream ID.
+          */
+         prog_data->control_data_format = GEN7_GS_CONTROL_DATA_FORMAT_GSCTL_SID;
+
+         /* We only have to emit control bits if we are using streams */
+         if (shader_prog && shader_prog->Geom.UsesStreams)
+            c.control_data_bits_per_vertex = 2;
+         else
+            c.control_data_bits_per_vertex = 0;
+      } else {
+         /* When the output type is triangle_strip or line_strip, EndPrimitive()
+          * may be used to terminate the current strip and start a new one
+          * (similar to primitive restart), and outputting data to multiple
+          * streams is not supported.  So we configure the hardware to interpret
+          * the control data as EndPrimitive information (a.k.a. "cut bits").
+          */
+         prog_data->control_data_format = GEN7_GS_CONTROL_DATA_FORMAT_GSCTL_CUT;
+
+         /* We only need to output control data if the shader actually calls
+          * EndPrimitive().
+          */
+         c.control_data_bits_per_vertex =
+            shader->info.gs.uses_end_primitive ? 1 : 0;
+      }
+   } else {
+      /* There are no control data bits in gen6. */
+      c.control_data_bits_per_vertex = 0;
+
+      /* If it is using transform feedback, enable it */
+      if (shader->info.has_transform_feedback_varyings)
+         prog_data->gen6_xfb_enabled = true;
+      else
+         prog_data->gen6_xfb_enabled = false;
+   }
+   c.control_data_header_size_bits =
+      shader->info.gs.vertices_out * c.control_data_bits_per_vertex;
+
+   /* 1 HWORD = 32 bytes = 256 bits */
+   prog_data->control_data_header_size_hwords =
+      ALIGN(c.control_data_header_size_bits, 256) / 256;
+
+   /* Compute the output vertex size.
+    *
+    * From the Ivy Bridge PRM, Vol2 Part1 7.2.1.1 STATE_GS - Output Vertex
+    * Size (p168):
+    *
+    *     [0,62] indicating [1,63] 16B units
+    *
+    *     Specifies the size of each vertex stored in the GS output entry
+    *     (following any Control Header data) as a number of 128-bit units
+    *     (minus one).
+    *
+    *     Programming Restrictions: The vertex size must be programmed as a
+    *     multiple of 32B units with the following exception: Rendering is
+    *     disabled (as per SOL stage state) and the vertex size output by the
+    *     GS thread is 16B.
+    *
+    *     If rendering is enabled (as per SOL state) the vertex size must be
+    *     programmed as a multiple of 32B units. In other words, the only time
+    *     software can program a vertex size with an odd number of 16B units
+    *     is when rendering is disabled.
+    *
+    * Note: B=bytes in the above text.
+    *
+    * It doesn't seem worth the extra trouble to optimize the case where the
+    * vertex size is 16B (especially since this would require special-casing
+    * the GEN assembly that writes to the URB).  So we just set the vertex
+    * size to a multiple of 32B (2 vec4's) in all cases.
+    *
+    * The maximum output vertex size is 62*16 = 992 bytes (31 hwords).  We
+    * budget that as follows:
+    *
+    *   512 bytes for varyings (a varying component is 4 bytes and
+    *             gl_MaxGeometryOutputComponents = 128)
+    *    16 bytes overhead for VARYING_SLOT_PSIZ (each varying slot is 16
+    *             bytes)
+    *    16 bytes overhead for gl_Position (we allocate it a slot in the VUE
+    *             even if it's not used)
+    *    32 bytes overhead for gl_ClipDistance (we allocate it 2 VUE slots
+    *             whenever clip planes are enabled, even if the shader doesn't
+    *             write to gl_ClipDistance)
+    *    16 bytes overhead since the VUE size must be a multiple of 32 bytes
+    *             (see below)--this causes up to 1 VUE slot to be wasted
+    *   400 bytes available for varying packing overhead
+    *
+    * Worst-case varying packing overhead is 3/4 of a varying slot (12 bytes)
+    * per interpolation type, so this is plenty.
+    *
+    */
+   unsigned output_vertex_size_bytes = prog_data->base.vue_map.num_slots * 16;
+   assert(compiler->devinfo->gen == 6 ||
+          output_vertex_size_bytes <= GEN7_MAX_GS_OUTPUT_VERTEX_SIZE_BYTES);
+   prog_data->output_vertex_size_hwords =
+      ALIGN(output_vertex_size_bytes, 32) / 32;
+
+   /* Compute URB entry size.  The maximum allowed URB entry size is 32k.
+    * That divides up as follows:
+    *
+    *     64 bytes for the control data header (cut indices or StreamID bits)
+    *   4096 bytes for varyings (a varying component is 4 bytes and
+    *              gl_MaxGeometryTotalOutputComponents = 1024)
+    *   4096 bytes overhead for VARYING_SLOT_PSIZ (each varying slot is 16
+    *              bytes/vertex and gl_MaxGeometryOutputVertices is 256)
+    *   4096 bytes overhead for gl_Position (we allocate it a slot in the VUE
+    *              even if it's not used)
+    *   8192 bytes overhead for gl_ClipDistance (we allocate it 2 VUE slots
+    *              whenever clip planes are enabled, even if the shader doesn't
+    *              write to gl_ClipDistance)
+    *   4096 bytes overhead since the VUE size must be a multiple of 32
+    *              bytes (see above)--this causes up to 1 VUE slot to be wasted
+    *   8128 bytes available for varying packing overhead
+    *
+    * Worst-case varying packing overhead is 3/4 of a varying slot per
+    * interpolation type, which works out to 3072 bytes, so this would allow
+    * us to accommodate 2 interpolation types without any danger of running
+    * out of URB space.
+    *
+    * In practice, the risk of running out of URB space is very small, since
+    * the above figures are all worst-case, and most of them scale with the
+    * number of output vertices.  So we'll just calculate the amount of space
+    * we need, and if it's too large, fail to compile.
+    *
+    * The above is for gen7+ where we have a single URB entry that will hold
+    * all the output. In gen6, we will have to allocate URB entries for every
+    * vertex we emit, so our URB entries only need to be large enough to hold
+    * a single vertex. Also, gen6 does not have a control data header.
+    */
+   unsigned output_size_bytes;
+   if (compiler->devinfo->gen >= 7) {
+      output_size_bytes =
+         prog_data->output_vertex_size_hwords * 32 * shader->info.gs.vertices_out;
+      output_size_bytes += 32 * prog_data->control_data_header_size_hwords;
+   } else {
+      output_size_bytes = prog_data->output_vertex_size_hwords * 32;
+   }
+
+   /* Broadwell stores "Vertex Count" as a full 8 DWord (32 byte) URB output,
+    * which comes before the control header.
+    */
+   if (compiler->devinfo->gen >= 8)
+      output_size_bytes += 32;
+
+   assert(output_size_bytes >= 1);
+   int max_output_size_bytes = GEN7_MAX_GS_URB_ENTRY_SIZE_BYTES;
+   if (compiler->devinfo->gen == 6)
+      max_output_size_bytes = GEN6_MAX_GS_URB_ENTRY_SIZE_BYTES;
+   if (output_size_bytes > max_output_size_bytes)
+      return false;
+
+
+   /* URB entry sizes are stored as a multiple of 64 bytes in gen7+ and
+    * a multiple of 128 bytes in gen6.
+    */
+   if (compiler->devinfo->gen >= 7)
+      prog_data->base.urb_entry_size = ALIGN(output_size_bytes, 64) / 64;
+   else
+      prog_data->base.urb_entry_size = ALIGN(output_size_bytes, 128) / 128;
+
+   prog_data->output_topology =
+      get_hw_prim_for_gl_prim(shader->info.gs.output_primitive);
+
+   /* The GLSL linker will have already matched up GS inputs and the outputs
+    * of prior stages.  The driver does extend VS outputs in some cases, but
+    * only for legacy OpenGL or Gen4-5 hardware, neither of which offer
+    * geometry shader support.  So we can safely ignore that.
+    *
+    * For SSO pipelines, we use a fixed VUE map layout based on variable
+    * locations, so we can rely on rendezvous-by-location making this work.
+    *
+    * However, we need to ignore VARYING_SLOT_PRIMITIVE_ID, as it's not
+    * written by previous stages and shows up via payload magic.
+    */
+   GLbitfield64 inputs_read =
+      shader->info.inputs_read & ~VARYING_BIT_PRIMITIVE_ID;
+   brw_compute_vue_map(compiler->devinfo,
+                       &c.input_vue_map, inputs_read,
+                       shader->info.separate_shader);
+
+   /* GS inputs are read from the VUE 256 bits (2 vec4's) at a time, so we
+    * need to program a URB read length of ceiling(num_slots / 2).
+    */
+   prog_data->base.urb_read_length = (c.input_vue_map.num_slots + 1) / 2;
+
+   /* Now that prog_data setup is done, we are ready to actually compile the
+    * program.
+    */
+
    if (compiler->devinfo->gen >= 7) {
       /* Compile the geometry shader in DUAL_OBJECT dispatch mode, if we can do
        * so without spilling. If the GS invocations count > 1, then we can't use
@@ -618,7 +821,7 @@ brw_compile_gs(const struct brw_compiler *compiler, void *log_data,
           likely(!(INTEL_DEBUG & DEBUG_NO_DUAL_OBJECT_GS))) {
          prog_data->base.dispatch_mode = DISPATCH_MODE_4X2_DUAL_OBJECT;
 
-         vec4_gs_visitor v(compiler, log_data, c, prog_data, shader,
+         vec4_gs_visitor v(compiler, log_data, &c, prog_data, shader,
                            mem_ctx, true /* no_spills */, shader_time_index);
          if (v.run()) {
             vec4_generator g(compiler, log_data, &prog_data->base, mem_ctx,
@@ -660,11 +863,11 @@ brw_compile_gs(const struct brw_compiler *compiler, void *log_data,
    const unsigned *ret = NULL;
 
    if (compiler->devinfo->gen >= 7)
-      gs = new vec4_gs_visitor(compiler, log_data, c, prog_data,
+      gs = new vec4_gs_visitor(compiler, log_data, &c, prog_data,
                                shader, mem_ctx, false /* no_spills */,
                                shader_time_index);
    else
-      gs = new gen6_gs_visitor(compiler, log_data, c, prog_data, shader_prog,
+      gs = new gen6_gs_visitor(compiler, log_data, &c, prog_data, shader_prog,
                                shader, mem_ctx, false /* no_spills */,
                                shader_time_index);