[Mesa-dev] [PATCH 3/3] i965/fs: Consider MOV.SAT to interfere if it has a source modifier.

[Ian Romanick]

This patch is

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

On 02/11/2015 02:54 PM, Matt Turner wrote:
> The saturate propagation pass recognizes that the second instruction
> below does not interfere with an attempt to propagate the saturate
> modifier from instruction 3 to 1.
> 
>  1:  add(8)     dst0   src0  src1
>  2:  mov.sat(8) dst1   dst0
>  3:  mov.sat(8) dst2   dst0
> 
> Unfortunately, we did not consider the case of instruction 2 having a
> source modifier on dst0. Take for instance:
> 
>  1:  add(8)     dst0   src0  src1
>  2:  mov.sat(8) dst1  -dst0
>  3:  mov.sat(8) dst2   dst0
> 
> Consider such an instruction to interfere. Increase instruction counts
> in Anomaly 2, which could be a bug fix depending on the values the first
> instruction produces.
> 
> Cc: <mesa-stable at lists.freedesktop.org>
> ---
>  .../dri/i965/brw_fs_saturate_propagation.cpp       | 12 ++++--
>  .../dri/i965/test_fs_saturate_propagation.cpp      | 44 ++++++++++++++++++++++
>  2 files changed, 52 insertions(+), 4 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_saturate_propagation.cpp b/src/mesa/drivers/dri/i965/brw_fs_saturate_propagation.cpp
> index bc51661..e406c28 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_saturate_propagation.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_saturate_propagation.cpp
> @@ -81,12 +81,16 @@ opt_saturate_propagation_local(fs_visitor *v, bblock_t *block)
>              break;
>           }
>           for (int i = 0; i < scan_inst->sources; i++) {
> -            if ((scan_inst->opcode != BRW_OPCODE_MOV || !scan_inst->saturate) &&
> -                scan_inst->src[i].file == GRF &&
> +            if (scan_inst->src[i].file == GRF &&
>                  scan_inst->src[i].reg == inst->src[0].reg &&
>                  scan_inst->src[i].reg_offset == inst->src[0].reg_offset) {
> -               interfered = true;
> -               break;
> +               if (scan_inst->opcode != BRW_OPCODE_MOV ||
> +                   !scan_inst->saturate ||
> +                   scan_inst->src[0].abs ||
> +                   scan_inst->src[0].negate) {
> +                  interfered = true;
> +                  break;
> +               }
>              }
>           }
>  
> diff --git a/src/mesa/drivers/dri/i965/test_fs_saturate_propagation.cpp b/src/mesa/drivers/dri/i965/test_fs_saturate_propagation.cpp
> index f897bdd..6f762bc 100644
> --- a/src/mesa/drivers/dri/i965/test_fs_saturate_propagation.cpp
> +++ b/src/mesa/drivers/dri/i965/test_fs_saturate_propagation.cpp
> @@ -393,3 +393,47 @@ TEST_F(saturate_propagation_test, intervening_dest_write)
>     EXPECT_EQ(BRW_OPCODE_MOV, instruction(block0, 2)->opcode);
>     EXPECT_TRUE(instruction(block0, 2)->saturate);
>  }
> +
> +TEST_F(saturate_propagation_test, mul_neg_mov_sat_mov_sat)
> +{
> +   fs_reg dst0 = v->vgrf(glsl_type::float_type);
> +   fs_reg dst1 = v->vgrf(glsl_type::float_type);
> +   fs_reg dst2 = v->vgrf(glsl_type::float_type);
> +   fs_reg src0 = v->vgrf(glsl_type::float_type);
> +   fs_reg src1 = v->vgrf(glsl_type::float_type);
> +   v->emit(BRW_OPCODE_MUL, dst0, src0, src1);
> +   dst0.negate = true;
> +   v->emit(BRW_OPCODE_MOV, dst1, dst0)
> +      ->saturate = true;
> +   dst0.negate = false;
> +   v->emit(BRW_OPCODE_MOV, dst2, dst0)
> +      ->saturate = true;
> +
> +   /* = Before =
> +    *
> +    * 0: mul(8)        dst0  src0  src1
> +    * 1: mov.sat(8)    dst1  -dst0
> +    * 2: mov.sat(8)    dst2  dst0
> +    *
> +    * = After =
> +    * (no changes)
> +    */
> +
> +   v->calculate_cfg();
> +   bblock_t *block0 = v->cfg->blocks[0];
> +
> +   EXPECT_EQ(0, block0->start_ip);
> +   EXPECT_EQ(2, block0->end_ip);
> +
> +   EXPECT_FALSE(saturate_propagation(v));
> +   EXPECT_EQ(0, block0->start_ip);
> +   EXPECT_EQ(2, block0->end_ip);
> +   EXPECT_EQ(BRW_OPCODE_MUL, instruction(block0, 0)->opcode);
> +   EXPECT_FALSE(instruction(block0, 0)->saturate);
> +   EXPECT_FALSE(instruction(block0, 0)->src[1].negate);
> +   EXPECT_EQ(BRW_OPCODE_MOV, instruction(block0, 1)->opcode);
> +   EXPECT_TRUE(instruction(block0, 1)->saturate);
> +   EXPECT_TRUE(instruction(block0, 1)->src[0].negate);
> +   EXPECT_EQ(BRW_OPCODE_MOV, instruction(block0, 2)->opcode);
> +   EXPECT_TRUE(instruction(block0, 2)->saturate);
> +}
>