1 files changed, 134 insertions, 0 deletions
diff --git a/src/compiler/nir/nir_lower_pntc_ytransform.c b/src/compiler/nir/nir_lower_pntc_ytransform.c
new file mode 100644
index 00000000000..f83d4650d4e
--- /dev/null
+++ b/src/compiler/nir/nir_lower_pntc_ytransform.c
@@ -0,0 +1,134 @@
+/*
+ * Copyright © 2020 Igalia S.L.
+ *
+ * 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"
+#include "program/prog_instruction.h"
+
+/* Lower gl_PointCoord to account for user requested point-coord origin
+ * and for whether draw buffer is flipped.
+ */
+
+typedef struct {
+   const gl_state_index16 *pntc_state_tokens;
+   nir_shader             *shader;
+   nir_builder             b;
+   nir_variable           *pntc_transform;
+} lower_pntc_ytransform_state;
+
+static nir_ssa_def *
+get_pntc_transform(lower_pntc_ytransform_state *state)
+{
+   if (state->pntc_transform == NULL) {
+      /* NOTE: name must be prefixed w/ "gl_" to trigger slot based
+       * special handling in uniform setup:
+       */
+      nir_variable *var = nir_variable_create(state->shader,
+                                              nir_var_uniform,
+                                              glsl_vec4_type(),
+                                              "gl_PntcYTransform");
+
+      var->num_state_slots = 1;
+      var->state_slots = ralloc_array(var, nir_state_slot, 1);
+      var->state_slots[0].swizzle = SWIZZLE_XYZW;
+      memcpy(var->state_slots[0].tokens, state->pntc_state_tokens,
+             sizeof(var->state_slots[0].tokens));
+      var->data.how_declared = nir_var_hidden;
+      state->pntc_transform = var;
+   }
+   return nir_load_var(&state->b, state->pntc_transform);
+}
+
+static void
+lower_load_pointcoord(lower_pntc_ytransform_state *state,
+                      nir_intrinsic_instr *intr)
+{
+   nir_builder *b = &state->b;
+   b->cursor = nir_after_instr(&intr->instr);
+
+   nir_ssa_def *pntc = &intr->dest.ssa;
+   nir_ssa_def *transform = get_pntc_transform(state);
+   nir_ssa_def *y = nir_channel(b, pntc, 1);
+   /* The offset is 1 if we're flipping, 0 otherwise. */
+   nir_ssa_def *offset = nir_channel(b, transform, 1);
+   /* Flip the sign of y if we're flipping. */
+   nir_ssa_def *scaled = nir_fmul(b, y, nir_channel(b, transform, 0));
+
+   /* Reassemble the vector. */
+   nir_ssa_def *flipped_pntc = nir_vec2(b,
+                                        nir_channel(b, pntc, 0),
+                                        nir_fadd(b, offset, scaled));
+
+   nir_ssa_def_rewrite_uses_after(&intr->dest.ssa, nir_src_for_ssa(flipped_pntc),
+                                  flipped_pntc->parent_instr);
+}
+
+static void
+lower_pntc_ytransform_block(lower_pntc_ytransform_state *state,
+                            nir_block *block)
+{
+   nir_foreach_instr_safe(instr, block) {
+      if (instr->type == nir_instr_type_intrinsic) {
+         nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+         if (intr->intrinsic == nir_intrinsic_load_deref) {
+            nir_deref_instr *deref = nir_src_as_deref(intr->src[0]);
+            nir_variable *var = nir_deref_instr_get_variable(deref);
+
+            if (var->data.mode == nir_var_shader_in &&
+                var->data.location == VARYING_SLOT_PNTC) {
+                lower_load_pointcoord(state, intr);
+            }
+         }
+      }
+   }
+}
+
+bool
+nir_lower_pntc_ytransform(nir_shader *shader,
+                          const gl_state_index16 pntc_state_tokens[][STATE_LENGTH])
+{
+    if (!shader->options->lower_wpos_pntc)
+        return false;
+
+   lower_pntc_ytransform_state state = {
+      .pntc_state_tokens = *pntc_state_tokens,
+      .shader = shader,
+      .pntc_transform = NULL,
+   };
+
+   assert(shader->info.stage == MESA_SHADER_FRAGMENT);
+
+   nir_foreach_function(function, shader) {
+      if (function->impl) {
+         nir_builder_init(&state.b, function->impl);
+
+         nir_foreach_block(block, function->impl) {
+            lower_pntc_ytransform_block(&state, block);
+         }
+         nir_metadata_preserve(function->impl, nir_metadata_block_index |
+                                               nir_metadata_dominance);
+      }
+   }
+
+   return state.pntc_transform != NULL;
+}