st/glsl_to_tgsi: swizzle PROGRAM_OUTPUTs correctly in src_register translation

This is required for reading directly from fragment shader stencil and depth
outputs.

Reviewed-by: Marek Olšák <[email protected]>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index 978dc46401b..8a247ea68d7 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -5383,9 +5383,19 @@ src_register(struct st_translate *t, const st_src_reg *reg)
 
    case PROGRAM_TEMPORARY:
    case PROGRAM_ARRAY:
-   case PROGRAM_OUTPUT:
       return ureg_src(dst_register(t, reg->file, reg->index, reg->array_id));
 
+   case PROGRAM_OUTPUT: {
+      struct ureg_dst dst = dst_register(t, reg->file, reg->index, reg->array_id);
+      assert(dst.WriteMask != 0);
+      unsigned shift = ffs(dst.WriteMask) - 1;
+      return ureg_swizzle(ureg_src(dst),
+                          shift,
+                          MIN2(shift + 1, 3),
+                          MIN2(shift + 2, 3),
+                          MIN2(shift + 3, 3));
+   }
+
    case PROGRAM_UNIFORM:
       assert(reg->index >= 0);
       return reg->index < t->num_constants ?