[Mesa-dev] [PATCH 4/6] nir/lower_tex: support for lowering RECT textures

[Rob Clark]

From: Rob Clark <robclark at freedesktop.org>

v2: comments/suggestions from Ilia and Eric, split out get_texture_size()
helper so we can use it in the next commit for clamping RECT textures.

Signed-off-by: Rob Clark <robclark at freedesktop.org>
---
 src/glsl/nir/nir.h           |  7 +++++
 src/glsl/nir/nir_lower_tex.c | 62 +++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 4600fb0..3c908b9 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1843,6 +1843,13 @@ typedef struct nir_lower_tex_options {
     * sampler types a texture projector is lowered.
     */
    unsigned lower_txp;
+
+   /**
+    * If true, lower rect textures to 2D, using txs to fetch the
+    * texture dimensions and dividing the texture coords by the
+    * texture dims to normalize.
+    */
+   bool lower_rect;
 } nir_lower_tex_options;
 
 void nir_lower_tex(nir_shader *shader,
diff --git a/src/glsl/nir/nir_lower_tex.c b/src/glsl/nir/nir_lower_tex.c
index 281fc9f..a71a5c5 100644
--- a/src/glsl/nir/nir_lower_tex.c
+++ b/src/glsl/nir/nir_lower_tex.c
@@ -22,9 +22,13 @@
  */
 
 /*
- * This lowering pass converts the coordinate division for texture projection
- * to be done in ALU instructions instead of asking the texture operation to
- * do so.
+ * This lowering pass supports (as configured via nir_lower_tex_options)
+ * various texture related conversions:
+ *   + texture projector lowering: converts the coordinate division for
+ *     texture projection to be done in ALU instructions instead of
+ *     asking the texture operation to do so.
+ *   + lowering RECT: converts the un-normalized RECT texture coordinates
+ *     to normalized coordinates with txs plus ALU instructions
  */
 
 #include "nir.h"
@@ -111,6 +115,55 @@ project_src(nir_builder *b, nir_tex_instr *tex)
    tex->num_srcs--;
 }
 
+static nir_ssa_def *
+get_texture_size(nir_builder *b, nir_tex_instr *tex)
+{
+   b->cursor = nir_before_instr(&tex->instr);
+
+   /* RECT textures should not be array: */
+   assert(!tex->is_array);
+
+   nir_tex_instr *txs;
+
+   txs = nir_tex_instr_create(b->shader, 1);
+   txs->op = nir_texop_txs;
+   txs->sampler_dim = GLSL_SAMPLER_DIM_RECT;
+   txs->sampler_index = tex->sampler_index;
+
+   /* only single src, the lod: */
+   txs->src[0].src = nir_src_for_ssa(nir_imm_int(b, 0));
+   txs->src[0].src_type = nir_tex_src_lod;
+
+   nir_ssa_dest_init(&txs->instr, &txs->dest, 3, NULL);
+   nir_builder_instr_insert(b, &txs->instr);
+
+   return nir_i2f(b, &txs->dest.ssa);
+}
+
+static void
+lower_rect(nir_builder *b, nir_tex_instr *tex)
+{
+   nir_ssa_def *txs = get_texture_size(b, tex);
+
+   nir_ssa_def *scalex = nir_frcp(b, nir_channel(b, txs, 0));
+   nir_ssa_def *scaley = nir_frcp(b, nir_channel(b, txs, 1));
+   nir_ssa_def *scale  = nir_vec2(b, scalex, scaley);
+
+   /* Walk through the sources normalizing the requested arguments. */
+   for (unsigned i = 0; i < tex->num_srcs; i++) {
+      if (tex->src[i].src_type != nir_tex_src_coord)
+         continue;
+
+      nir_ssa_def *coords =
+         nir_ssa_for_src(b, tex->src[i].src, tex->coord_components);
+      nir_instr_rewrite_src(&tex->instr,
+                            &tex->src[i].src,
+                            nir_src_for_ssa(nir_fmul(b, coords, scale)));
+   }
+
+   tex->sampler_dim = GLSL_SAMPLER_DIM_2D;
+}
+
 static bool
 nir_lower_tex_block(nir_block *block, void *void_state)
 {
@@ -127,6 +180,9 @@ nir_lower_tex_block(nir_block *block, void *void_state)
       if (lower_txp)
          project_src(b, tex);
 
+      if ((tex->sampler_dim == GLSL_SAMPLER_DIM_RECT) &&
+          state->options->lower_rect)
+         lower_rect(b, tex);
    }
 
    return true;
-- 
2.4.3