[Mesa-dev] [PATCH] i965: Fix GPU hangs on Broadwell in shaders with some control flow.

[Matt Turner]

On Thu, May 8, 2014 at 4:44 PM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> According to the documentation, we need to set the source 0 register
> type to IMM for flow control instructions that have both JIP and UIP.
>
> Fixes GPU hangs in approximately 10 Piglit tests, 5 es3conform tests,
> Unigine Crypt, a WebGL raytracer demo, and several Steam titles.
>
> Cc: "10.2" <mesa-stable at lists.freedesktop.org>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75478
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75878
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76939
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
>  src/mesa/drivers/dri/i965/gen8_generator.cpp | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/gen8_generator.cpp b/src/mesa/drivers/dri/i965/gen8_generator.cpp
> index dd434a7..faca9c0 100644
> --- a/src/mesa/drivers/dri/i965/gen8_generator.cpp
> +++ b/src/mesa/drivers/dri/i965/gen8_generator.cpp
> @@ -422,6 +422,7 @@ gen8_generator::IF(unsigned predicate)
>  {
>     gen8_instruction *inst = next_inst(BRW_OPCODE_IF);
>     gen8_set_dst(brw, inst, vec1(retype(brw_null_reg(), BRW_REGISTER_TYPE_D)));
> +   gen8_set_src0(brw, inst, brw_imm_d(0));
>     gen8_set_exec_size(inst, default_state.exec_size);
>     gen8_set_pred_control(inst, predicate);
>     gen8_set_mask_control(inst, BRW_MASK_ENABLE);
> @@ -435,6 +436,7 @@ gen8_generator::ELSE()
>  {
>     gen8_instruction *inst = next_inst(BRW_OPCODE_ELSE);
>     gen8_set_dst(brw, inst, retype(brw_null_reg(), BRW_REGISTER_TYPE_D));
> +   gen8_set_src0(brw, inst, brw_imm_d(0));
>     gen8_set_mask_control(inst, BRW_MASK_ENABLE);
>     push_if_stack(inst);
>     return inst;
> @@ -456,6 +458,7 @@ gen8_generator::ENDIF()
>
>     gen8_instruction *endif_inst = next_inst(BRW_OPCODE_ENDIF);
>     gen8_set_mask_control(endif_inst, BRW_MASK_ENABLE);
> +   gen8_set_src0(brw, endif_inst, brw_imm_d(0));

Else and endif don't have UIP, so they don't need this.

With those hunks removed:

Reviewed-by: Matt Turner <mattst88 at gmail.com>