glsl: use hash instead of exec_list in copy propagation

This change makes copy propagation pass faster. Complete link time
spent in test case attached to bug 94477 goes down to ~400 secs from
over 500 secs on my HSW machine. Does not fix the actual issue but
brings down the total. No regressions seen in CI.

v2: do not leak hash_table structure

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
1 file changed