[Mesa-dev] [PATCH] i965/disasm: Properly decode branch_ctrl (gen8+)

[Kenneth Graunke]

On Tuesday, November 18, 2014 12:35:55 PM Ben Widawsky wrote:
> Add support for decoding the new branch control bit. I saw two things wrong with
> the existing code.
> 
> 1. It didn't bother trying to decode the bit.
> -  While we do not *intentionally* emit this bit today, I think it's interesting
>    to see if we somehow ended up with the bit set. It may also be useful in the
>    future.
> 
> 2. It seemed to be the wrong bit.
> -  The docs are pretty poor wrt which bit this actually occupies. To me, it
>    /looks/ like it should be bit 28. I am not sure where Ken got 30 from. I
>    verified it should be 28 by looking at the simulator code.

Yeah, it sure looks like 28 to me...I must've botched it when typing up the
tables.

One comment below.

> I also added the most basic support for GOTO simply so we don't need to remember
> to change the function in the future.
> 
> Cc: Kenneth Graunke <kenneth at whitecape.org>
> Signed-off-by: Ben Widawsky <ben at bwidawsk.net>
> ---
>  src/mesa/drivers/dri/i965/brw_defines.h |  1 +
>  src/mesa/drivers/dri/i965/brw_disasm.c  | 29 ++++++++++++++++++++++++++---
>  src/mesa/drivers/dri/i965/brw_inst.h    |  2 +-
>  3 files changed, 28 insertions(+), 4 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
> index 53cd75e..ed94bcc 100644
> --- a/src/mesa/drivers/dri/i965/brw_defines.h
> +++ b/src/mesa/drivers/dri/i965/brw_defines.h
> @@ -820,6 +820,7 @@ enum opcode {
>     BRW_OPCODE_MSAVE =	44,  /**< Pre-Gen6 */
>     BRW_OPCODE_MRESTORE = 45, /**< Pre-Gen6 */
>     BRW_OPCODE_PUSH =	46,  /**< Pre-Gen6 */
> +   BRW_OPCODE_GOTO =	46,  /**< Gen8+    */
>     BRW_OPCODE_POP =	47,  /**< Pre-Gen6 */
>     BRW_OPCODE_WAIT =	48,
>     BRW_OPCODE_SEND =	49,
> diff --git a/src/mesa/drivers/dri/i965/brw_disasm.c b/src/mesa/drivers/dri/i965/brw_disasm.c
> index 53ec767..013058e 100644
> --- a/src/mesa/drivers/dri/i965/brw_disasm.c
> +++ b/src/mesa/drivers/dri/i965/brw_disasm.c
> @@ -131,6 +131,18 @@ has_uip(struct brw_context *brw, enum opcode opcode)
>  }
>  
>  static bool
> +has_branch_ctrl(struct brw_context *brw, enum opcode opcode)
> +{
> +   if (brw->gen < 8)
> +      return false;
> +
> +   return opcode == BRW_OPCODE_IF ||
> +          opcode == BRW_OPCODE_ELSE ||
> +          opcode == BRW_OPCODE_GOTO ||
> +          opcode == BRW_OPCODE_ENDIF;
> +}

I don't think ENDIF has BranchCtrl.  With that removed, this is:

Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: This is a digitally signed message part.
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20141119/68e0b87e/attachment.sig>