nir: add lowering pass for glBitmap

Signed-off-by: Rob Clark <robclark@freedesktop.org>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

src/compiler/Makefile.sources

@@ -186,6 +186,7 @@ NIR_FILES = \
 	nir/nir_liveness.c \
 	nir/nir_lower_alu_to_scalar.c \
 	nir/nir_lower_atomics.c \
+	nir/nir_lower_bitmap.c \
 	nir/nir_lower_clamp_color_outputs.c \
 	nir/nir_lower_clip.c \
 	nir/nir_lower_double_ops.c \

src/compiler/nir/nir.h

@@ -2398,6 +2398,13 @@ typedef struct nir_lower_drawpixels_options {
 void nir_lower_drawpixels(nir_shader *shader,
                           const nir_lower_drawpixels_options *options);
 
+typedef struct nir_lower_bitmap_options {
+   unsigned sampler;
+   bool swizzle_xxxx;
+} nir_lower_bitmap_options;
+
+void nir_lower_bitmap(nir_shader *shader, const nir_lower_bitmap_options *options);
+
 void nir_lower_atomics(nir_shader *shader,
                        const struct gl_shader_program *shader_program);
 void nir_lower_to_source_mods(nir_shader *shader);

src/compiler/nir/nir_lower_bitmap.c

@@ -0,0 +1,139 @@
+/*
+ * Copyright © 2015 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+/* Lower glBitmap().
+ *
+ * This is based on the logic in st_get_bitmap_shader() in TGSI compiler.
+ * From st_cb_bitmap.c:
+ *
+ *    glBitmaps are drawn as textured quads.  The user's bitmap pattern
+ *    is stored in a texture image.  An alpha8 texture format is used.
+ *    The fragment shader samples a bit (texel) from the texture, then
+ *    discards the fragment if the bit is off.
+ *
+ *    Note that we actually store the inverse image of the bitmap to
+ *    simplify the fragment program.  An "on" bit gets stored as texel=0x0
+ *    and an "off" bit is stored as texel=0xff.  Then we kill the
+ *    fragment if the negated texel value is less than zero.
+ *
+ * Note that the texture format will be, according to what driver supports,
+ * in order of preference (with swizzle):
+ *
+ *    I8_UNORM - .xxxx
+ *    A8_UNORM - .000x
+ *    L8_UNORM - .xxx1
+ *
+ * If L8_UNORM, options->swizzle_xxxx is true.  Otherwise we can just use
+ * the .w comp.
+ *
+ * Run before nir_lower_io.
+ */
+
+static nir_variable *
+get_texcoord(nir_shader *shader)
+{
+   nir_variable *texcoord = NULL;
+
+   /* find gl_TexCoord, if it exists: */
+   nir_foreach_variable(var, &shader->inputs) {
+      if (var->data.location == VARYING_SLOT_TEX0) {
+         texcoord = var;
+         break;
+      }
+   }
+
+   /* otherwise create it: */
+   if (texcoord == NULL) {
+      texcoord = nir_variable_create(shader,
+                                     nir_var_shader_in,
+                                     glsl_vec4_type(),
+                                     "gl_TexCoord");
+      texcoord->data.location = VARYING_SLOT_TEX0;
+   }
+
+   return texcoord;
+}
+
+static void
+lower_bitmap(nir_shader *shader, nir_builder *b,
+             const nir_lower_bitmap_options *options)
+{
+   nir_ssa_def *texcoord;
+   nir_tex_instr *tex;
+   nir_ssa_def *cond;
+   nir_intrinsic_instr *discard;
+
+   texcoord = nir_load_var(b, get_texcoord(shader));
+
+   tex = nir_tex_instr_create(shader, 1);
+   tex->op = nir_texop_tex;
+   tex->sampler_dim = GLSL_SAMPLER_DIM_2D;
+   tex->coord_components = 2;
+   tex->sampler_index = options->sampler;
+   tex->texture_index = options->sampler;
+   tex->dest_type = nir_type_float;
+   tex->src[0].src = nir_src_for_ssa(texcoord);
+
+   nir_ssa_dest_init(&tex->instr, &tex->dest, 4, 32, NULL);
+   nir_builder_instr_insert(b, &tex->instr);
+
+   /* kill if tex != 0.0.. take .x or .w channel according to format: */
+   cond = nir_f2b(b, nir_channel(b, &tex->dest.ssa,
+                  options->swizzle_xxxx ? 0 : 3));
+
+   discard = nir_intrinsic_instr_create(shader, nir_intrinsic_discard_if);
+   discard->src[0] = nir_src_for_ssa(cond);
+   nir_builder_instr_insert(b, &discard->instr);
+}
+
+static void
+lower_bitmap_impl(nir_function_impl *impl,
+                  const nir_lower_bitmap_options *options)
+{
+   nir_builder b;
+
+   nir_builder_init(&b, impl);
+   b.cursor = nir_before_cf_list(&impl->body);
+
+   lower_bitmap(impl->function->shader, &b, options);
+
+   nir_metadata_preserve(impl, nir_metadata_block_index |
+                               nir_metadata_dominance);
+}
+
+void
+nir_lower_bitmap(nir_shader *shader,
+                 const nir_lower_bitmap_options *options)
+{
+   nir_function *function;
+
+   assert(shader->stage == MESA_SHADER_FRAGMENT);
+
+   function = nir_shader_get_entrypoint(shader);
+
+   if (function->impl)
+      lower_bitmap_impl(function->impl, options);
+}