[Mesa-dev] [PATCH] nir/spirv: handle if's with same label in both branches

[Jason Ekstrand]

On Thu, Aug 24, 2017 at 8:16 AM, Juan A. Suarez Romero <jasuarez at igalia.com>
wrote:

> When a conditional branch has the same labels in the "if" part and in the
> "else" part, then we have the same cfg block, and it must be handled
> once.
>
> Fixes:
> dEQP-VK.spirv_assembly.instruction.compute.conditional_branch.same_labels*
> dEQP-VK.spirv_assembly.instruction.graphics.conditional_branch.same_
> labels*
> ---
>  src/compiler/spirv/vtn_cfg.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/src/compiler/spirv/vtn_cfg.c b/src/compiler/spirv/vtn_cfg.c
> index 03c452cb31..bfca7043cc 100644
> --- a/src/compiler/spirv/vtn_cfg.c
> +++ b/src/compiler/spirv/vtn_cfg.c
> @@ -356,8 +356,11 @@ vtn_cfg_walk_blocks(struct vtn_builder *b, struct
> list_head *cf_list,
>                                                    switch_case,
> switch_break,
>                                                    loop_break, loop_cont);
>
> -         if (if_stmt->then_type == vtn_branch_type_none &&
> -             if_stmt->else_type == vtn_branch_type_none) {
> +         if (then_block == else_block) {
> +            block = then_block;
> +            continue;
>

This isn't quite sufficient.  This needs to be handled the same way as
OpBranch.  In particular,

block->branch_type = if_stmt->then_type;
if (block->branch_type == vtn_branch_type_none) {
   block = then_block;
   continue;
} else {
   return;
}


> +         } else if (if_stmt->then_type == vtn_branch_type_none &&
> +                    if_stmt->else_type == vtn_branch_type_none) {
>              /* Neither side of the if is something we can short-circuit.
> */
>              assert((*block->merge & SpvOpCodeMask) ==
> SpvOpSelectionMerge);
>              struct vtn_block *merge_block =
> --
> 2.13.5
>
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