[Mesa-dev] [PATCH v3 35/48] intel/eu: Make automatic exec sizes a configurable option

[Iago Toral]

On Wed, 2017-10-25 at 16:26 -0700, Jason Ekstrand wrote:
> We have had a feature in codegen for some time that tries to
> automatically infer the execution size of an instruction from the
> width
> of its destination.  For things such as fixed function GS, clipper,
> and
> SF programs, this is very useful because they tend to have lots of
> hand-rolled register setup and trying to specify the exec size all
> the
> time would be prohibitive.  For things that come from a higher-level
> IR,
> however, it's easier to just set the right size all the time and the
> automatic exec sizes can, in fact, cause problems.  This commit makes
> it
> optional while enabling it by default.
> ---
>  src/intel/compiler/brw_eu.c      |  1 +
>  src/intel/compiler/brw_eu.h      | 10 ++++++++++
>  src/intel/compiler/brw_eu_emit.c | 32 ++++++++++++++++++----------
> ----
>  3 files changed, 29 insertions(+), 14 deletions(-)
> 
> diff --git a/src/intel/compiler/brw_eu.c
> b/src/intel/compiler/brw_eu.c
> index b0bdc38..bc297a2 100644
> --- a/src/intel/compiler/brw_eu.c
> +++ b/src/intel/compiler/brw_eu.c
> @@ -296,6 +296,7 @@ brw_init_codegen(const struct gen_device_info
> *devinfo,
>     memset(p, 0, sizeof(*p));
>  
>     p->devinfo = devinfo;
> +   p->automatic_exec_sizes = true;
>     /*
>      * Set the initial instruction store array size to 1024, if found
> that
>      * isn't enough, then it will double the store size at
> brw_next_insn()
> diff --git a/src/intel/compiler/brw_eu.h
> b/src/intel/compiler/brw_eu.h
> index 8e597b2..8abebeb 100644
> --- a/src/intel/compiler/brw_eu.h
> +++ b/src/intel/compiler/brw_eu.h
> @@ -65,6 +65,16 @@ struct brw_codegen {
>     bool compressed_stack[BRW_EU_MAX_INSN_STACK];
>     brw_inst *current;
>  
> +   /** Whether or not the user wants automatic exec sizes
> +    *
> +    * If true, codegen will try to automatically infer the exec size
> of an
> +    * instruction from the width of the destination register.  If
> false, it
> +    * will take whatever is set by brw_set_default_exec_size
> verbatim.
> +    *
> +    * This is set to true by default in brw_init_codegen.
> +    */
> +   bool automatic_exec_sizes;
> +
>     bool single_program_flow;
>     const struct gen_device_info *devinfo;
>  
> diff --git a/src/intel/compiler/brw_eu_emit.c
> b/src/intel/compiler/brw_eu_emit.c
> index fae74cf..902914f 100644
> --- a/src/intel/compiler/brw_eu_emit.c
> +++ b/src/intel/compiler/brw_eu_emit.c
> @@ -141,22 +141,26 @@ brw_set_dest(struct brw_codegen *p, brw_inst
> *inst, struct brw_reg dest)
>  
>     /* Generators should set a default exec_size of either 8 (SIMD4x2
> or SIMD8)
>      * or 16 (SIMD16), as that's normally correct.  However, when
> dealing with
> -    * small registers, we automatically reduce it to match the
> register size.
> -    *
> -    * In platforms that support fp64 we can emit instructions with a
> width of
> -    * 4 that need two SIMD8 registers and an exec_size of 8 or 16.
> In these
> -    * cases we need to make sure that these instructions have their
> exec sizes
> -    * set properly when they are emitted and we can't rely on this
> code to fix
> -    * it.
> +    * small registers, it can be useful for us toautomatically 

to automatically

> reduce it to
> +    * match the register size.
>      */
> -   bool fix_exec_size;
> -   if (devinfo->gen >= 6)
> -      fix_exec_size = dest.width < BRW_EXECUTE_4;
> -   else
> -      fix_exec_size = dest.width < BRW_EXECUTE_8;
> +   if (p->automatic_exec_sizes) {
> +      /*
> +       * In platforms that support fp64 we can emit instructions
> with a width
> +       * of 4 that need two SIMD8 registers and an exec_size of 8 or
> 16. In
> +       * these cases we need to make sure that these instructions
> have their
> +       * exec sizes set properly when they are emitted and we can't
> rely on
> +       * this code to fix it.
> +       */
> +      bool fix_exec_size;
> +      if (devinfo->gen >= 6)
> +         fix_exec_size = dest.width < BRW_EXECUTE_4;
> +      else
> +         fix_exec_size = dest.width < BRW_EXECUTE_8;
>  
> -   if (fix_exec_size)
> -      brw_inst_set_exec_size(devinfo, inst, dest.width);
> +      if (fix_exec_size)
> +         brw_inst_set_exec_size(devinfo, inst, dest.width);
> +   }
>  }
>  
>  void