nir/lower_tex: add support to clamp texture coords

Some hardware needs to clamp texture coordinates to [0.0, 1.0] in the
shader to emulate GL_CLAMP.  This is added to lower_tex_proj since, in
the case of projected coords, the clamping needs to happen *after*
projection.

v2: comments/suggestions from Ilia and Eric, use txs to get texture size
and clamp RECT textures to their dimensions rather than [0.0, 1.0] to
avoid having to lower RECT textures to 2D.

Signed-off-by: Rob Clark <[email protected]>
Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 3c908b9f295..255d45585db 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1850,6 +1850,24 @@ typedef struct nir_lower_tex_options {
     * texture dims to normalize.
     */
    bool lower_rect;
+
+   /**
+    * To emulate certain texture wrap modes, this can be used
+    * to saturate the specified tex coord to [0.0, 1.0].  The
+    * bits are according to sampler #, ie. if, for example:
+    *
+    *   (conf->saturate_s & (1 << n))
+    *
+    * is true, then the s coord for sampler n is saturated.
+    *
+    * Note that clamping must happen *after* projector lowering
+    * so any projected texture sample instruction with a clamped
+    * coordinate gets automatically lowered, regardless of the
+    * 'lower_txp' setting.
+    */
+   unsigned saturate_s;
+   unsigned saturate_t;
+   unsigned saturate_r;
 } nir_lower_tex_options;
 
 void nir_lower_tex(nir_shader *shader,