[Mesa-dev] [PATCH v2] spirv: fix visiting inner loops with same break/continue block

[Jason Ekstrand]

I don't think this does the right thing in the switch fall-through case but
it will at least fail with a reasonable assert instead of just doing the
wrong thing.

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

On Tue, May 15, 2018 at 3:00 AM, Samuel Pitoiset <samuel.pitoiset at gmail.com>
wrote:

> We should stop walking through the CFG when the inner loop's
> break block ends up as the same block as the outer loop's
> continue block because we are already going to visit it.
>
> This fixes the following assertion which ends up by crashing
> in RADV or ANV:
>
> SPIR-V parsing FAILED:
> In file ../src/compiler/spirv/vtn_cfg.c:381
> block->node.link.next == NULL
> 0 bytes into the SPIR-V binary
>
> This also fixes a crash with a camera shader from SteamVR.
>
> v2: make use of vtn_get_branch_type() and add an assertion
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106090
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106504
> CC: 18.0 18.1 <mesa-stable at lists.freedesktop.org>
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
>  src/compiler/spirv/vtn_cfg.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/src/compiler/spirv/vtn_cfg.c b/src/compiler/spirv/vtn_cfg.c
> index e7d2f9ea61..ad4374112e 100644
> --- a/src/compiler/spirv/vtn_cfg.c
> +++ b/src/compiler/spirv/vtn_cfg.c
> @@ -374,6 +374,19 @@ vtn_cfg_walk_blocks(struct vtn_builder *b, struct
> list_head *cf_list,
>           vtn_cfg_walk_blocks(b, &loop->cont_body, new_loop_cont, NULL,
> NULL,
>                               new_loop_break, NULL, block);
>
> +         enum vtn_branch_type branch_type =
> +            vtn_get_branch_type(b, new_loop_break, switch_case,
> switch_break,
> +                                loop_break, loop_cont);
> +
> +         if (branch_type != vtn_branch_type_none) {
> +            /* Stop walking through the CFG when this inner loop's break
> block
> +             * ends up as the same block as the outer loop's continue
> block
> +             * because we are already going to visit it.
> +             */
> +            vtn_assert(branch_type == vtn_branch_type_loop_continue);
> +            return;
> +         }
> +
>           block = new_loop_break;
>           continue;
>        }
> --
> 2.17.0
>
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