[Mesa-dev] [PATCH 1/3] glsl: don't drop intructions from unreachable terminators continue branch

[tournier.elie]

With the small nitpick from Eric, the series is:
Reviewed-by: Elie Tournier <elie.tournier at collabora.com>

On 14 September 2017 at 05:47, Timothy Arceri <tarceri at itsqueeze.com> wrote:
> These instruction will be executed on every iteration of the loop
> we cannot drop them.
> ---
>  src/compiler/glsl/loop_analysis.h   |  7 +++++++
>  src/compiler/glsl/loop_controls.cpp | 15 +++++++++++++++
>  src/compiler/glsl/loop_unroll.cpp   |  7 -------
>  3 files changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/src/compiler/glsl/loop_analysis.h b/src/compiler/glsl/loop_analysis.h
> index 2894c6359b..0e1bfd8142 100644
> --- a/src/compiler/glsl/loop_analysis.h
> +++ b/src/compiler/glsl/loop_analysis.h
> @@ -27,20 +27,27 @@
>
>  #include "ir.h"
>  #include "util/hash_table.h"
>
>  /**
>   * Analyze and classify all variables used in all loops in the instruction list
>   */
>  extern class loop_state *
>  analyze_loop_variables(exec_list *instructions);
>
> +static inline bool
> +is_break(ir_instruction *ir)
> +{
> +   return ir != NULL && ir->ir_type == ir_type_loop_jump &&
> +      ((ir_loop_jump *) ir)->is_break();
> +}
> +
>
>  /**
>   * Fill in loop control fields
>   *
>   * Based on analysis of loop variables, this function tries to remove
>   * redundant sequences in the loop of the form
>   *
>   *  (if (expression bool ...) (break))
>   *
>   * For example, if it is provable that one loop exit condition will
> diff --git a/src/compiler/glsl/loop_controls.cpp b/src/compiler/glsl/loop_controls.cpp
> index 895954fc2d..2dff26aec0 100644
> --- a/src/compiler/glsl/loop_controls.cpp
> +++ b/src/compiler/glsl/loop_controls.cpp
> @@ -215,21 +215,36 @@ loop_control_visitor::visit_leave(ir_loop *ir)
>      * that are associated with a fixed iteration count, except for the one
>      * associated with the limiting terminator--that one needs to stay, since
>      * it terminates the loop.  Exception: if the loop still has a normative
>      * bound, then that terminates the loop, so we don't even need the limiting
>      * terminator.
>      */
>     foreach_in_list(loop_terminator, t, &ls->terminators) {
>        if (t->iterations < 0)
>           continue;
>
> +      exec_list *branch_instructions;
>        if (t != ls->limiting_terminator) {
> +         ir_instruction *ir_if_last = (ir_instruction *)
> +           t->ir->then_instructions.get_tail();
> +         if (is_break(ir_if_last)) {
> +            branch_instructions = &t->ir->else_instructions;
> +         } else {
> +            branch_instructions = &t->ir->then_instructions;
> +            assert(is_break(ir_if_last));
> +         }
> +
> +         exec_list copy_list;
> +         copy_list.make_empty();
> +         clone_ir_list(ir, &copy_list, branch_instructions);
> +
> +         t->ir->insert_before(&copy_list);
>           t->ir->remove();
>
>           assert(ls->num_loop_jumps > 0);
>           ls->num_loop_jumps--;
>
>           this->progress = true;
>        }
>     }
>
>     return visit_continue;
> diff --git a/src/compiler/glsl/loop_unroll.cpp b/src/compiler/glsl/loop_unroll.cpp
> index dbb3fa2fa5..7f601295a1 100644
> --- a/src/compiler/glsl/loop_unroll.cpp
> +++ b/src/compiler/glsl/loop_unroll.cpp
> @@ -46,27 +46,20 @@ public:
>     void splice_post_if_instructions(ir_if *ir_if, exec_list *splice_dest);
>
>     loop_state *state;
>
>     bool progress;
>     const struct gl_shader_compiler_options *options;
>  };
>
>  } /* anonymous namespace */
>
> -static bool
> -is_break(ir_instruction *ir)
> -{
> -   return ir != NULL && ir->ir_type == ir_type_loop_jump
> -                    && ((ir_loop_jump *) ir)->is_break();
> -}
> -
>  class loop_unroll_count : public ir_hierarchical_visitor {
>  public:
>     int nodes;
>     bool unsupported_variable_indexing;
>     bool array_indexed_by_induction_var_with_exact_iterations;
>     /* If there are nested loops, the node count will be inaccurate. */
>     bool nested_loop;
>
>     loop_unroll_count(exec_list *list, loop_variable_state *ls,
>                       const struct gl_shader_compiler_options *options)
> --
> 2.13.5
>
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