i965: Copy propagate before doing variable index lowering.

The scalar backend currently doesn't support variable indexing on
temporary arrays, but it does support it on uniform arrays, and
some stages support it for input arrays.  Make sure these are
propagated through before exploding indirects into piles of
if-ladders unnecessarily.

On Broadwell, no instruction count change in shader-db.

total cycles in shared programs: 80675652 -> 80674928 (-0.00%)
cycles in affected programs: 649972 -> 649248 (-0.11%)
helped: 386
HURT: 165

This will help avoid code quality regressions in a future commit.

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>

diff --git a/src/mesa/drivers/dri/i965/brw_link.cpp b/src/mesa/drivers/dri/i965/brw_link.cpp
index 3bb04fa6effc1ca105fc65c93d74ddb66e1e8dc5..76c580b4648802de018829dae0d4d389cc1af1b3 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_link.cpp
+++ b/src/mesa/drivers/dri/i965/brw_link.cpp
@@ -130,6 +130,8 @@ process_glsl_ir(gl_shader_stage stage,
    lower_noise(shader->ir);
    lower_quadop_vector(shader->ir, false);
 
+   do_copy_propagation(shader->ir);
+
    bool lowered_variable_indexing =
       lower_variable_index_to_cond_assign((gl_shader_stage)stage,
                                           shader->ir,