On Wed, Jun 29, 2016 at 2:04 PM, Ian Romanick <i...@freedesktop.org> wrote:
> From: Ian Romanick <ian.d.roman...@intel.com>
>
> This uses one less instruction.
Add FBH to the list of stupid instructions.
> Signed-off-by: Ian Romanick <ian.d.roman...@intel.com>
> ---
> src/mesa/drivers/dri/i965/brw_fs.h | 4 ++++
> src/mesa/drivers/dri/i965/brw_fs_generator.cpp | 3 +++
> src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 26
> +++++++++++++++++++++++-
> src/mesa/drivers/dri/i965/brw_vec4.h | 4 ++++
> src/mesa/drivers/dri/i965/brw_vec4_generator.cpp | 3 +++
> src/mesa/drivers/dri/i965/brw_vec4_nir.cpp | 22 ++++++++++++++++++++
> 6 files changed, 61 insertions(+), 1 deletion(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.h
> b/src/mesa/drivers/dri/i965/brw_fs.h
> index 4237197..22ce092 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.h
> +++ b/src/mesa/drivers/dri/i965/brw_fs.h
> @@ -237,6 +237,10 @@ public:
> nir_tex_instr *instr);
> void nir_emit_jump(const brw::fs_builder &bld,
> nir_jump_instr *instr);
> + void nir_emit_find_msb_using_lzd(const brw::fs_builder &bld,
> + const fs_reg &result,
> + const fs_reg &src,
> + bool is_signed);
> fs_reg get_nir_src(const nir_src &src);
> fs_reg get_nir_src_imm(const nir_src &src);
> fs_reg get_nir_dest(const nir_dest &dest);
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> index d25d26a..bda4a26 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> @@ -1761,6 +1761,9 @@ fs_generator::generate_code(const cfg_t *cfg, int
> dispatch_width)
> /* FBL only supports UD type for dst. */
> brw_FBL(p, retype(dst, BRW_REGISTER_TYPE_UD), src[0]);
> break;
> + case BRW_OPCODE_LZD:
> + brw_LZD(p, dst, src[0]);
> + break;
> case BRW_OPCODE_CBIT:
> assert(devinfo->gen >= 7);
> /* CBIT only supports UD type for dst. */
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> index b3f5dfd..f15bf3e 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> @@ -617,6 +617,25 @@ fs_visitor::optimize_frontfacing_ternary(nir_alu_instr
> *instr,
> }
>
> void
> +fs_visitor::nir_emit_find_msb_using_lzd(const fs_builder &bld,
> + const fs_reg &result,
> + const fs_reg &src,
> + bool is_signed)
> +{
> + fs_inst *inst;
> +
> + bld.LZD(retype(result, BRW_REGISTER_TYPE_UD), src);
> +
> + /* LZD counts from the MSB side, while GLSL's findMSB() wants the count
> + * from the LSB side. Subtract the result from 31 to convert the MSB
> + * count into an LSB count. If no bits are set, LZD will return 32.
> + * 31-32 = -1, which is exactly what findMSB() is supposed to return.
> + */
> + inst = bld.ADD(result, retype(result, BRW_REGISTER_TYPE_D),
> brw_imm_d(31));
> + inst->src[0].negate = true;
> +}
I'd personally be inclined to just inline these functions. I know they
grow somewhat in the next patches... whatever your preference is.
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