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/*
* Copyright © 2020 Microsoft Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include "nir.h"
#include "nir_builder.h"
static bool
nir_scale_fdiv_instr(nir_builder *b, nir_instr *instr, UNUSED void *_data)
{
if (instr->type != nir_instr_type_alu)
return false;
nir_alu_instr *alu = nir_instr_as_alu(instr);
if (alu->op != nir_op_fdiv || alu->src[0].src.ssa->bit_size != 32)
return false;
b->cursor = nir_before_instr(&alu->instr);
nir_ssa_def *orig_a = nir_ssa_for_alu_src(b, alu, 0);
nir_ssa_def *orig_b = nir_ssa_for_alu_src(b, alu, 1);
nir_ssa_def *fabs = nir_fabs(b, orig_b);
nir_ssa_def *big = nir_flt(b, nir_imm_int(b, 0x7e800000), fabs);
nir_ssa_def *small = nir_flt(b, fabs, nir_imm_int(b, 0x00800000));
nir_ssa_def *scaled_down_a = nir_fmul_imm(b, orig_a, 0.25);
nir_ssa_def *scaled_down_b = nir_fmul_imm(b, orig_b, 0.25);
nir_ssa_def *scaled_up_a = nir_fmul_imm(b, orig_a, 16777216.0);
nir_ssa_def *scaled_up_b = nir_fmul_imm(b, orig_b, 16777216.0);
nir_ssa_def *final_a =
nir_bcsel(b, big, scaled_down_a,
(nir_bcsel(b, small, scaled_up_a, orig_a)));
nir_ssa_def *final_b =
nir_bcsel(b, big, scaled_down_b,
(nir_bcsel(b, small, scaled_up_b, orig_b)));
nir_ssa_def *new_div = nir_fdiv(b, final_a, final_b);
nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa, new_div);
return true;
}
/** Scale both sides of an fdiv if needed to prevent denorm flushing
*
* This may be needed to satisfy the precision requirements of OpenCL. When
* fdiv is lowered to frcp+fmul, denorm flushing may cause the frcp to return
* zero even for finite floats. This multiplies both sides of an fdiv by a
* constant, if needed, to prevent such flushing.
*/
bool
nir_scale_fdiv(nir_shader *shader)
{
return nir_shader_instructions_pass(shader, nir_scale_fdiv_instr,
nir_metadata_block_index |
nir_metadata_dominance,
NULL);
}
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