Matt Turner <matts...@gmail.com> writes:
> 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.It seems to grow quite a bit in PATCH 16, and it's used in multiple places, right? How about we keep it factored out but make it a stand-alone function instead of a visitor method? It doesn't look like it uses *any* internal or external data structures of fs_visitor, it doesn't even dereference the 'this' pointer at all AFAICT, so you could likely improve encapsulation somewhat by making it a static function local to the brw_*_nir.cpp source files. > _______________________________________________ > mesa-dev mailing list > mesa-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/mesa-dev
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