Mesa (master): vc4: Clamp the shadow comparison value.

[Eric Anholt]

Module: Mesa
Branch: master
Commit: 08d51487e3b8cfb14ca2ece9545b2e2ed344e3cc
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=08d51487e3b8cfb14ca2ece9545b2e2ed344e3cc

Author: Eric Anholt <eric at anholt.net>
Date:   Mon Nov  7 12:25:47 2016 -0800

vc4: Clamp the shadow comparison value.

Fixes piglit glsl-fs-shadow2D-clamp-z.

Cc: <mesa-stable at lists.freedesktop.org>

---

 src/gallium/drivers/vc4/vc4_program.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/gallium/drivers/vc4/vc4_program.c b/src/gallium/drivers/vc4/vc4_program.c
index 86f71f6..abd20a5 100644
--- a/src/gallium/drivers/vc4/vc4_program.c
+++ b/src/gallium/drivers/vc4/vc4_program.c
@@ -495,6 +495,15 @@ ntq_emit_tex(struct vc4_compile *c, nir_tex_instr *instr)
                 struct qreg u0 = qir_uniform_f(c, 0.0f);
                 struct qreg u1 = qir_uniform_f(c, 1.0f);
                 if (c->key->tex[unit].compare_mode) {
+                        /* From the GL_ARB_shadow spec:
+                         *
+                         *     "Let Dt (D subscript t) be the depth texture
+                         *      value, in the range [0, 1].  Let R be the
+                         *      interpolated texture coordinate clamped to the
+                         *      range [0, 1]."
+                         */
+                        compare = qir_SAT(c, compare);
+
                         switch (c->key->tex[unit].compare_func) {
                         case PIPE_FUNC_NEVER:
                                 depth_output = qir_uniform_f(c, 0.0f);