nir: add lowering pass for y-transform

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

@@ -208,6 +208,7 @@ NIR_FILES = \
 	nir/nir_lower_vars_to_ssa.c \
 	nir/nir_lower_var_copies.c \
 	nir/nir_lower_vec_to_movs.c \
+	nir/nir_lower_wpos_ytransform.c \
 	nir/nir_metadata.c \
 	nir/nir_move_vec_src_uses_to_dest.c \
 	nir/nir_normalize_cubemap_coords.c \

src/compiler/nir/nir.h

@@ -2374,6 +2374,17 @@ void nir_lower_two_sided_color(nir_shader *shader);
 
 void nir_lower_clamp_color_outputs(nir_shader *shader);
 
+typedef struct nir_lower_wpos_ytransform_options {
+   int state_tokens[5];
+   bool fs_coord_origin_upper_left :1;
+   bool fs_coord_origin_lower_left :1;
+   bool fs_coord_pixel_center_integer :1;
+   bool fs_coord_pixel_center_half_integer :1;
+} nir_lower_wpos_ytransform_options;
+
+bool nir_lower_wpos_ytransform(nir_shader *shader,
+                               const nir_lower_wpos_ytransform_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_wpos_ytransform.c

@@ -0,0 +1,310 @@
+/*
+ * 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 gl_FragCoord (and fddy) to account for driver's requested coordinate-
+ * origin and pixel-center vs. shader.  If transformation is required, a
+ * gl_FbWposYTransform uniform is inserted (with the specified state-slots)
+ * and additional instructions are inserted to transform gl_FragCoord (and
+ * fddy src arg).
+ *
+ * This is based on the logic in emit_wpos()/emit_wpos_adjustment() in TGSI
+ * compiler.
+ *
+ * Run before nir_lower_io.
+ */
+
+typedef struct {
+   const nir_lower_wpos_ytransform_options *options;
+   nir_shader   *shader;
+   nir_builder   b;
+   nir_variable *transform;
+} lower_wpos_ytransform_state;
+
+static nir_ssa_def *
+get_transform(lower_wpos_ytransform_state *state)
+{
+   if (state->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_FbWposYTransform");
+
+      var->num_state_slots = 1;
+      var->state_slots = ralloc_array(var, nir_state_slot, 1);
+      memcpy(var->state_slots[0].tokens, state->options->state_tokens,
+             sizeof(var->state_slots[0].tokens));
+
+      state->transform = var;
+   }
+   return nir_load_var(&state->b, state->transform);
+}
+
+/* NIR equiv of TGSI CMP instruction: */
+static nir_ssa_def *
+nir_cmp(nir_builder *b, nir_ssa_def *src0, nir_ssa_def *src1, nir_ssa_def *src2)
+{
+   return nir_bcsel(b, nir_flt(b, src0, nir_imm_float(b, 0.0)), src1, src2);
+}
+
+/* see emit_wpos_adjustment() in st_mesa_to_tgsi.c */
+static void
+emit_wpos_adjustment(lower_wpos_ytransform_state *state,
+                     nir_intrinsic_instr *intr,
+                     bool invert, float adjX, float adjY[2])
+{
+   nir_builder *b = &state->b;
+   nir_variable *fragcoord = intr->variables[0]->var;
+   nir_ssa_def *wpostrans, *wpos_temp, *wpos_temp_y, *wpos_input;
+
+   assert(intr->dest.is_ssa);
+
+   b->cursor = nir_before_instr(&intr->instr);
+
+   wpostrans = get_transform(state);
+   wpos_input = nir_load_var(b, fragcoord);
+
+   /* First, apply the coordinate shift: */
+   if (adjX || adjY[0] || adjY[1]) {
+      if (adjY[0] != adjY[1]) {
+         /* Adjust the y coordinate by adjY[1] or adjY[0] respectively
+          * depending on whether inversion is actually going to be applied
+          * or not, which is determined by testing against the inversion
+          * state variable used below, which will be either +1 or -1.
+          */
+         nir_ssa_def *adj_temp;
+
+         adj_temp = nir_cmp(b,
+                            nir_channel(b, wpostrans, invert ? 2 : 0),
+                            nir_imm_vec4(b, adjX, adjY[0], 0.0f, 0.0f),
+                            nir_imm_vec4(b, adjX, adjY[1], 0.0f, 0.0f));
+
+         wpos_temp = nir_fadd(b, wpos_input, adj_temp);
+      } else {
+         wpos_temp = nir_fadd(b,
+                              wpos_input,
+                              nir_imm_vec4(b, adjX, adjY[0], 0.0f, 0.0f));
+      }
+      wpos_input = wpos_temp;
+   } else {
+      /* MOV wpos_temp, input[wpos]
+       */
+      wpos_temp = wpos_input;
+   }
+
+   /* Now the conditional y flip: STATE_FB_WPOS_Y_TRANSFORM.xy/zw will be
+    * inversion/identity, or the other way around if we're drawing to an FBO.
+    */
+   if (invert) {
+      /* MAD wpos_temp.y, wpos_input, wpostrans.xxxx, wpostrans.yyyy
+       */
+      wpos_temp_y = nir_ffma(b,
+                             nir_channel(b, wpos_temp, 1),
+                             nir_channel(b, wpostrans, 0),
+                             nir_channel(b, wpostrans, 1));
+   } else {
+      /* MAD wpos_temp.y, wpos_input, wpostrans.zzzz, wpostrans.wwww
+       */
+      wpos_temp_y = nir_ffma(b,
+                             nir_channel(b, wpos_temp, 1),
+                             nir_channel(b, wpostrans, 2),
+                             nir_channel(b, wpostrans, 3));
+   }
+
+   wpos_temp = nir_vec4(b,
+                        nir_channel(b, wpos_temp, 0),
+                        wpos_temp_y,
+                        nir_channel(b, wpos_temp, 2),
+                        nir_channel(b, wpos_temp, 3));
+
+   nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(wpos_temp));
+}
+
+static void
+lower_fragcoord(lower_wpos_ytransform_state *state, nir_intrinsic_instr *intr)
+{
+   const nir_lower_wpos_ytransform_options *options = state->options;
+   nir_variable *fragcoord = intr->variables[0]->var;
+   float adjX = 0.0f;
+   float adjY[2] = { 0.0f, 0.0f };
+   bool invert = false;
+
+   /* Based on logic in emit_wpos():
+    *
+    * Query the pixel center conventions supported by the pipe driver and set
+    * adjX, adjY to help out if it cannot handle the requested one internally.
+    *
+    * The bias of the y-coordinate depends on whether y-inversion takes place
+    * (adjY[1]) or not (adjY[0]), which is in turn dependent on whether we are
+    * drawing to an FBO (causes additional inversion), and whether the the pipe
+    * driver origin and the requested origin differ (the latter condition is
+    * stored in the 'invert' variable).
+    *
+    * For height = 100 (i = integer, h = half-integer, l = lower, u = upper):
+    *
+    * center shift only:
+    * i -> h: +0.5
+    * h -> i: -0.5
+    *
+    * inversion only:
+    * l,i -> u,i: ( 0.0 + 1.0) * -1 + 100 = 99
+    * l,h -> u,h: ( 0.5 + 0.0) * -1 + 100 = 99.5
+    * u,i -> l,i: (99.0 + 1.0) * -1 + 100 = 0
+    * u,h -> l,h: (99.5 + 0.0) * -1 + 100 = 0.5
+    *
+    * inversion and center shift:
+    * l,i -> u,h: ( 0.0 + 0.5) * -1 + 100 = 99.5
+    * l,h -> u,i: ( 0.5 + 0.5) * -1 + 100 = 99
+    * u,i -> l,h: (99.0 + 0.5) * -1 + 100 = 0.5
+    * u,h -> l,i: (99.5 + 0.5) * -1 + 100 = 0
+    */
+
+   if (fragcoord->data.origin_upper_left) {
+      /* Fragment shader wants origin in upper-left */
+      if (options->fs_coord_origin_upper_left) {
+         /* the driver supports upper-left origin */
+      } else if (options->fs_coord_origin_lower_left) {
+         /* the driver supports lower-left origin, need to invert Y */
+         invert = true;
+      } else {
+         unreachable("invalid options");
+      }
+   } else {
+      /* Fragment shader wants origin in lower-left */
+      if (options->fs_coord_origin_lower_left) {
+         /* the driver supports lower-left origin */
+      } else if (options->fs_coord_origin_upper_left) {
+         /* the driver supports upper-left origin, need to invert Y */
+         invert = true;
+      } else {
+         unreachable("invalid options");
+      }
+   }
+
+   if (fragcoord->data.pixel_center_integer) {
+      /* Fragment shader wants pixel center integer */
+      if (options->fs_coord_pixel_center_integer) {
+         /* the driver supports pixel center integer */
+         adjY[1] = 1.0f;
+      } else if (options->fs_coord_pixel_center_half_integer) {
+         /* the driver supports pixel center half integer, need to bias X,Y */
+         adjX = -0.5f;
+         adjY[0] = -0.5f;
+         adjY[1] = 0.5f;
+      } else {
+         unreachable("invalid options");
+      }
+   } else {
+      /* Fragment shader wants pixel center half integer */
+      if (options->fs_coord_pixel_center_half_integer) {
+         /* the driver supports pixel center half integer */
+      } else if (options->fs_coord_pixel_center_integer) {
+         /* the driver supports pixel center integer, need to bias X,Y */
+         adjX = adjY[0] = adjY[1] = 0.5f;
+      } else {
+         unreachable("invalid options");
+      }
+   }
+
+   emit_wpos_adjustment(state, intr, invert, adjX, adjY);
+}
+
+/* turns 'fddy(p)' into 'fddy(fmul(p, transform.x))' */
+static void
+lower_fddy(lower_wpos_ytransform_state *state, nir_alu_instr *fddy)
+{
+   nir_builder *b = &state->b;
+   nir_ssa_def *p, *pt, *trans;
+
+   b->cursor = nir_before_instr(&fddy->instr);
+
+   p = nir_ssa_for_alu_src(b, fddy, 0);
+   trans = get_transform(state);
+   pt = nir_fmul(b, p, nir_channel(b, trans, 0));
+
+   nir_instr_rewrite_src(&fddy->instr,
+                         &fddy->src[0].src,
+                         nir_src_for_ssa(pt));
+}
+
+static bool
+lower_wpos_ytransform_block(lower_wpos_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_var) {
+            nir_deref_var *dvar = intr->variables[0];
+            nir_variable *var = dvar->var;
+
+            if (strcmp(var->name, "gl_FragCoord") == 0) {
+               /* gl_FragCoord should not have array/struct deref's: */
+               assert(dvar->deref.child == NULL);
+               lower_fragcoord(state, intr);
+            }
+         }
+      } else if (instr->type == nir_instr_type_alu) {
+         nir_alu_instr *alu = nir_instr_as_alu(instr);
+         if (alu->op == nir_op_fddy)
+            lower_fddy(state, alu);
+      }
+   }
+
+   return true;
+}
+
+static void
+lower_wpos_ytransform_impl(lower_wpos_ytransform_state *state, nir_function_impl *impl)
+{
+   nir_builder_init(&state->b, impl);
+
+   nir_foreach_block(block, impl) {
+      lower_wpos_ytransform_block(state, block);
+   }
+   nir_metadata_preserve(impl, nir_metadata_block_index |
+                               nir_metadata_dominance);
+}
+
+bool
+nir_lower_wpos_ytransform(nir_shader *shader,
+                          const nir_lower_wpos_ytransform_options *options)
+{
+   lower_wpos_ytransform_state state = {
+      .options = options,
+      .shader = shader,
+   };
+
+   assert(shader->stage == MESA_SHADER_FRAGMENT);
+
+   nir_foreach_function(function, shader) {
+      if (function->impl)
+         lower_wpos_ytransform_impl(&state, function->impl);
+   }
+
+   return state.transform != NULL;
+}