[Mesa-dev] [PATCH 11/21] glsl: Store ir_variable::ir_type in 8 bits instead of 32

[Matt Turner]

On Tue, May 27, 2014 at 7:49 PM, Ian Romanick <idr at freedesktop.org> wrote:
> From: Ian Romanick <ian.d.romanick at intel.com>
>
> No change in the peak ir_variable memory usage in a trimmed apitrace of
> dota2 on 64-bit.
>
> No change in the peak ir_variable memory usage in a trimmed apitrace of
> dota2 on 32-bit.
>
> Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
> ---
>  src/glsl/ir.h | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/src/glsl/ir.h b/src/glsl/ir.h
> index 7faee74..bc02f6e 100644
> --- a/src/glsl/ir.h
> +++ b/src/glsl/ir.h
> @@ -92,12 +92,13 @@ enum ir_node_type {
>   */
>  class ir_instruction : public exec_node {
>  private:
> -   enum ir_node_type ir_type;
> +   uint8_t ir_type;
>
>  public:
>     inline enum ir_node_type get_ir_type() const
>     {
> -      return this->ir_type;
> +      STATIC_ASSERT(ir_type_max < 256);
> +      return (enum ir_node_type) this->ir_type;
>     }
>
>     /**
> --
> 1.8.1.4

Instead of doing this, you can mark the enum type with the PACKED
attribute. I did this in a similar change in i965 already. See
http://lists.freedesktop.org/archives/mesa-dev/2014-February/054643.html

This way we still get enum type checking and warnings out of switch
statements and such.