On our hardware, indirect accesses can go through memory with no
bounds checking.
Marek
On Thu, Jun 28, 2018 at 12:46 AM, Ian Romanick <i...@freedesktop.org> wrote:
> From: Ian Romanick <ian.d.roman...@intel.com>
>
> That flow control may be trying to avoid invalid loads. On at least
> some platforms, those loads can also be expensive.
>
> No shader-db changes on any Intel platform (even with the later patch
> "intel/compiler: More peephole select").
>
> NOTE: I've tried to CC everyone whose drive might be affected by this
> change.
>
> Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
> Cc: Eric Anholt <e...@anholt.net>
> Cc: Rob Clark <robdcl...@gmail.com>
> Cc: Marek Olšák <marek.ol...@amd.com>
> ---
> src/compiler/nir/nir_opt_peephole_select.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/src/compiler/nir/nir_opt_peephole_select.c
> b/src/compiler/nir/nir_opt_peephole_select.c
> index 4ca4f80d788..920ced2137c 100644
> --- a/src/compiler/nir/nir_opt_peephole_select.c
> +++ b/src/compiler/nir/nir_opt_peephole_select.c
> @@ -58,7 +58,8 @@
> */
>
> static bool
> -block_check_for_allowed_instrs(nir_block *block, unsigned *count, bool
> alu_ok)
> +block_check_for_allowed_instrs(nir_block *block, unsigned *count,
> + gl_shader_stage stage, bool alu_ok)
> {
> nir_foreach_instr(instr, block) {
> switch (instr->type) {
> @@ -70,6 +71,13 @@ block_check_for_allowed_instrs(nir_block *block, unsigned
> *count, bool alu_ok)
> switch (intrin->variables[0]->var->data.mode) {
> case nir_var_shader_in:
> case nir_var_uniform:
> + /* Don't try to remove flow control around an indirect load
> + * because that flow control may be trying to avoid invalid
> + * loads.
> + */
> + if (nir_deref_has_indirect(stage, intrin->variables[0]))
> + return false;
> +
> break;
>
> default:
> @@ -168,8 +176,10 @@ nir_opt_peephole_select_block(nir_block *block,
> nir_shader *shader,
>
> /* ... and those blocks must only contain "allowed" instructions. */
> unsigned count = 0;
> - if (!block_check_for_allowed_instrs(then_block, &count, limit != 0) ||
> - !block_check_for_allowed_instrs(else_block, &count, limit != 0))
> + if (!block_check_for_allowed_instrs(then_block, &count,
> shader->info.stage,
> + limit != 0) ||
> + !block_check_for_allowed_instrs(else_block, &count,
> shader->info.stage,
> + limit != 0))
> return false;
>
> if (count > limit)
> --
> 2.14.4
>
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> mesa-dev@lists.freedesktop.org
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