On Wed, Apr 11, 2012 at 9:33 PM, Eric Anholt <e...@anholt.net> wrote:
> Cuts 8/1068 instructions from glyphy's fragment shaders on i965.
> ---
> src/glsl/opt_if_simplification.cpp | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/src/glsl/opt_if_simplification.cpp
> b/src/glsl/opt_if_simplification.cpp
> index 940dd08..7e88208 100644
> --- a/src/glsl/opt_if_simplification.cpp
> +++ b/src/glsl/opt_if_simplification.cpp
> @@ -66,6 +66,14 @@ do_if_simplification(exec_list *instructions)
> ir_visitor_status
> ir_if_simplification_visitor::visit_leave(ir_if *ir)
> {
> + /* If the if statement has nothing on either side, remove it. */
> + if (ir->then_instructions.is_empty() &&
> + ir->else_instructions.is_empty()) {
> + ir->remove();
> + this->made_progress = true;
> + return visit_continue;
> + }
> +
> /* FINISHME: Ideally there would be a way to note that the condition
> results
> * FINISHME: in a constant before processing both of the other subtrees.
> * FINISHME: This can probably be done with some flags, but it would take
> --
> 1.7.9.5
Follow on: If then_instructions is empty, is there any benefit in
inverting the if conditional and moving the else_instructions into the
place of then_instructions?
Matt
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