i965: Fix swizzling in vector splitting for the new FS backend.

We weren't smearing a component of a split RHS out to reach an unsplit
LHS's writemask, so gl_FragColor (always unsplit) would often get
uninitialized values.

Fixes: glsl-algebraic-add-add-1 (and probably many others).

1 files changed, 3 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_fs_vector_splitting.cpp b/src/mesa/drivers/dri/i965/brw_fs_vector_splitting.cpp
index d4da86b3b06..00d5c202485 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_vector_splitting.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_vector_splitting.cpp
@@ -281,6 +281,9 @@ ir_vector_splitting_visitor::visit_leave(ir_assignment *ir)
 
 	 if (rhs) {
 	    new_rhs = new(mem_ctx) ir_dereference_variable(rhs->components[i]);
+	    /* If we're writing into a writemask, smear it out to that channel. */
+	    if (!lhs)
+	       new_rhs = new(mem_ctx) ir_swizzle(new_rhs, i, i, i, i, i + 1);
 	 } else {
 	    new_rhs = new(mem_ctx) ir_swizzle(ir->rhs->clone(mem_ctx, NULL),
 					      i, i, i, i, 1);