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111 lines
4.1 KiB
C++
111 lines
4.1 KiB
C++
/*
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* The MIT License (MIT)
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*
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* Copyright (c) 2015-2024 Advanced Micro Devices, Inc. All rights reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <migraphx/rewrite_gelu.hpp>
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#include <migraphx/make_op.hpp>
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#include <migraphx/matcher.hpp>
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#include <migraphx/match/gelu_erf.hpp>
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#include <migraphx/match/gelu_tanh.hpp>
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#include <migraphx/common.hpp>
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namespace migraphx {
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inline namespace MIGRAPHX_INLINE_NS {
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/**
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* The replacement approximation is equivalent to:
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* GELU(x) ~= 0.5 * x * ( 1 + tanh( sqrt(2/M_PI) * (x + 0.044715 * x^3)))
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* You can rearrange to the form used in this by recognizing that
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* 1 + tanh(x) = (2) / (1 + exp(-2 * x)).
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* The fitting constant 0.044715 is from
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* A. Choudhury, ‘A simple approximation to the area under standard normal curve’, Mathematics and
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* Statistics, vol. 2, no. 3, pp. 147–149, 2014.
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*/
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void replace_with_tanh_exp_gelu(module& m, const match::matcher_result& r)
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{
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auto ins = r.result;
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auto x = r.instructions["x"];
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double const0 = -2. * sqrt(M_2_PI);
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double const1 = 0.044715 * const0;
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auto lit0 = m.add_literal(literal{shape{x->get_shape().type()}, {const0}});
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auto lit1 = m.add_literal(literal{shape{x->get_shape().type()}, {const1}});
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auto one = m.add_literal(literal{shape{x->get_shape().type()}, {1.0}});
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auto xb = insert_common_op(m, ins, make_op("mul"), {x, lit1});
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auto a = m.insert_instruction(ins, make_op("mul"), x, xb);
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auto b = insert_common_op(m, ins, make_op("add"), {a, lit0});
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auto u = m.insert_instruction(ins, make_op("mul"), x, b);
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auto emu = m.insert_instruction(ins, make_op("exp"), u);
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auto c = insert_common_op(m, ins, make_op("add"), {one, emu});
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auto y = m.insert_instruction(ins, make_op("div"), x, c);
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m.replace_instruction(ins, y);
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}
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/**
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* Finds erfGELU blocks using the Gaussian distribution and replaces them with the tanh_exp
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* approximation if the data type is fp16. TODO consider also for fp8 datatype.
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*/
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struct find_gelu_erf
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{
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auto matcher() const { return match::any_of(match::gelu_erf(), match::gelu_tanh()); }
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void apply(module& m, const match::matcher_result& r) const
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{
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auto x = r.instructions["x"];
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auto input_type = x->get_shape().type();
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std::set<migraphx::shape::type_t> convert_types = {migraphx::shape::half_type};
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if(not contains(convert_types, input_type))
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return;
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replace_with_tanh_exp_gelu(m, r);
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}
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};
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/**
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* Find tanhGELU blocks and replace them with a rearranged version that is less likely to overflow
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* and is more performant.
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*/
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struct find_tanh_fast_gelu
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{
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auto matcher() const { return match::gelu_tanh(); }
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void apply(module& m, const match::matcher_result& r) const
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{
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replace_with_tanh_exp_gelu(m, r);
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}
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};
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void rewrite_gelu::apply(module& m) const
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{
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if(fast_math)
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{
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match::find_matches(m, find_gelu_erf{});
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}
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else
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{
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match::find_matches(m, find_tanh_fast_gelu{});
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}
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}
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} // namespace MIGRAPHX_INLINE_NS
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} // namespace migraphx
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