[Mesa-dev] [PATCH 13/19] i965/fs: Only consider real sources when comparing instructions.

[Kenneth Graunke]

On 04/18/2014 11:56 AM, Matt Turner wrote:
> ---
>  src/mesa/drivers/dri/i965/brw_fs_cse.cpp | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)

I originally thought this needed to go earlier in the patch series,
since by this point you're emitting opcodes with more than 3 sources.
However, CSE ignores SHADER_OPCODE_LOAD_PAYLOAD, so this code will never
run for opcodes that could break.  So, it's probably fine.

> diff --git a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
> index 94f657d..e40567f 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_cse.cpp
> @@ -94,10 +94,20 @@ is_expression_commutative(enum opcode op)
>  }
>  
>  static bool
> -operands_match(enum opcode op, fs_reg *xs, fs_reg *ys)
> +operands_match(fs_inst *a, fs_inst *b)
>  {
> -   if (!is_expression_commutative(op)) {
> -      return xs[0].equals(ys[0]) && xs[1].equals(ys[1]) && xs[2].equals(ys[2]);
> +   fs_reg *xs = a->src;
> +   fs_reg *ys = b->src;
> +
> +   if (!is_expression_commutative(a->opcode)) {
> +      bool match = true;
> +      for (int i = 0; i < a->sources; i++) {
> +         if (!xs[i].equals(ys[i])) {
> +            match = false;
> +            break;
> +         }
> +      }
> +      return match;
>     } else {
>        return (xs[0].equals(ys[0]) && xs[1].equals(ys[1])) ||
>               (xs[1].equals(ys[0]) && xs[0].equals(ys[1]));

It strikes me as a bit asymmetric to have the first block handle an
arbitrary number of sources, and the second only check 0 and 1.  It
makes sense, since our commutative opcodes are all binops, but...

How about adding

      /* All commutative opcodes are binary operations. */
      assert(a->sources == 2 && b->sources == 2);

here in the commutative case?

> @@ -113,7 +123,8 @@ instructions_match(fs_inst *a, fs_inst *b)
>            a->predicate_inverse == b->predicate_inverse &&
>            a->conditional_mod == b->conditional_mod &&
>            a->dst.type == b->dst.type &&
> -          operands_match(a->opcode, a->src, b->src);
> +          a->sources == b->sources &&
> +          operands_match(a, b);
>  }
>  
>  bool
> 

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