[Mesa-dev] [PATCH 07/10] nir: return early when lowering a return at the end of a function

[Jason Ekstrand]

Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

On Mon, Apr 9, 2018 at 9:34 PM, Timothy Arceri <tarceri at itsqueeze.com>
wrote:

> Otherwise we create unused conditional return flags and things
> get unnecessarily ugly fast when lowering nested functions.
> ---
>  src/compiler/nir/nir_lower_returns.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/src/compiler/nir/nir_lower_returns.c
> b/src/compiler/nir/nir_lower_returns.c
> index 423192adb8a..e1ba5f2ad64 100644
> --- a/src/compiler/nir/nir_lower_returns.c
> +++ b/src/compiler/nir/nir_lower_returns.c
> @@ -27,6 +27,7 @@
>
>  struct lower_returns_state {
>     nir_builder builder;
> +   nir_function_impl *impl;
>

I think we could avoid this by looking at block->node.parent.  Meh.


>     struct exec_list *cf_list;
>     nir_loop *loop;
>     nir_variable *return_flag;
> @@ -180,6 +181,12 @@ lower_returns_in_block(nir_block *block, struct
> lower_returns_state *state)
>
>     nir_instr_remove(&jump->instr);
>
> +   /* If this is a return in the last block of the function there is
> nothing
> +    * more to do once its removed.
> +    */
> +   if (block == nir_impl_last_block(state->impl))
> +      return true;
> +
>     nir_builder *b = &state->builder;
>
>     /* Set the return flag */
> @@ -252,6 +259,7 @@ nir_lower_returns_impl(nir_function_impl *impl)
>  {
>     struct lower_returns_state state;
>
> +   state.impl = impl;
>     state.cf_list = &impl->body;
>     state.loop = NULL;
>     state.return_flag = NULL;
> --
> 2.17.0
>
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