i915g: use passthough shader for empty fragment programs

The hw doesn't like it - demos/shadowtex is broken. The emitted shader
isn't totally empty though, the depth write fixup gets emitted instead.
Maybe that one is somewhat fishy, too?

Idea for this patch from Jakob Bornecrantz.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/src/gallium/drivers/i915/i915_fpc_translate.c b/src/gallium/drivers/i915/i915_fpc_translate.c
index 9e20010..cd8219e 100644 (file)
--- a/src/gallium/drivers/i915/i915_fpc_translate.c
+++ b/src/gallium/drivers/i915/i915_fpc_translate.c
@@ -1174,15 +1174,27 @@ void
 i915_translate_fragment_program( struct i915_context *i915,
                                  struct i915_fragment_shader *fs)
 {
-   struct i915_fp_compile *p = i915_init_compile(i915, fs);
+   struct i915_fp_compile *p;
    const struct tgsi_token *tokens = fs->state.tokens;
-
-   i915_find_wpos_space(p);
+   struct tgsi_shader_info info;
 
 #if 0
    tgsi_dump(tokens, 0);
 #endif
 
+   tgsi_scan_shader(tokens, &info);
+
+   /* hw doesn't seem to like empty frag programs, even when the depth write
+    * fixup gets emitted below - may that one is fishy, too? */
+   if (info.num_instructions == 1) {
+      i915_use_passthrough_shader(fs);
+
+      return;
+   }
+
+   p = i915_init_compile(i915, fs);
+   i915_find_wpos_space(p);
+
    i915_translate_instructions(p, tokens);
    i915_fixup_depth_write(p);