st/glsl_to_tgsi: fix conditional assignments to packed shader outputs

Overriding the default (no-op) swizzle is clearly counter-productive,
since the whole point is putting the destination register as one of
the source operands so that it remains unmodified when the assignment
condition is false.

Fragment depth and stencil outputs are a special case due to how their
source swizzles are manipulated in translate_src when compiling to
TGSI.

Fixes dEQP-GLES2.functional.shaders.conditionals.if.*_vertex
Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Tested-by: Dieter Nützel <Dieter@nuetzel-hh.de>

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index f4870a1c606914988a89333dcf04d877d909ecb8..0daf5a14285924d24b50f8002a8de6aae9915188 100644 (file)
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -2897,7 +2897,15 @@ glsl_to_tgsi_visitor::emit_block_mov(ir_assignment *ir, const struct glsl_type *
    r->type = type->base_type;
    if (cond) {
       st_src_reg l_src = st_src_reg(*l);
-      l_src.swizzle = swizzle_for_size(type->vector_elements);
+
+      if (l_src.file == PROGRAM_OUTPUT &&
+          this->prog->Target == GL_FRAGMENT_PROGRAM_ARB &&
+          (l_src.index == FRAG_RESULT_DEPTH || l_src.index == FRAG_RESULT_STENCIL)) {
+         /* This is a special case because the source swizzles will be shifted
+          * later to account for the difference between GLSL (where they're
+          * plain floats) and TGSI (where they're Z and Y components). */
+         l_src.swizzle = SWIZZLE_XXXX;
+      }
 
       if (native_integers) {
          emit_asm(ir, TGSI_OPCODE_UCMP, *l, *cond,