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-rw-r--r--src/mesa/program/prog_execute.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/src/mesa/program/prog_execute.c b/src/mesa/program/prog_execute.c
index c70a1e344e5..77f842a1630 100644
--- a/src/mesa/program/prog_execute.c
+++ b/src/mesa/program/prog_execute.c
@@ -1651,6 +1651,14 @@ _mesa_execute_program(struct gl_context * ctx,
GLfloat texcoord[4], color[4];
fetch_vector4(&inst->SrcReg[0], machine, texcoord);
+ /* For TEX, texcoord.Q should not be used and its value should not
+ * matter (at most, we pass coord.xyz to texture3D() in GLSL).
+ * Set Q=1 so that FetchTexelDeriv() doesn't get a garbage value
+ * which is effectively what happens when the texcoord swizzle
+ * is .xyzz
+ */
+ texcoord[3] = 1.0f;
+
fetch_texel(ctx, machine, inst, texcoord, 0.0, color);
if (DEBUG_PROG) {