Jacques Lucke
eedcf1876a
This moves all multi-function related code in the `functions` module into a new `multi_function` namespace. This is similar to how there is a `lazy_function` namespace. The main benefit of this is that many types names that were prefixed with `MF` (for "multi function") can be simplified. There is also a common shorthand for the `multi_function` namespace: `mf`. This is also similar to lazy-functions where the shortened namespace is called `lf`.
48 lines
2.4 KiB
C++
48 lines
2.4 KiB
C++
/* SPDX-License-Identifier: GPL-2.0-or-later */
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#pragma once
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/** \file
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* \ingroup fn
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*
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* A #Procedure optimization pass takes an existing procedure and changes it in a way that
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* improves its performance when executed.
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*
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* Oftentimes it would also be possible to implement a specific optimization directly during
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* construction of the initial #Procedure. There is a trade-off between doing that or just
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* building a "simple" procedure and then optimizing it uses separate optimization passes.
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* - Doing optimizations directly during construction is typically faster than doing it as a
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* separate pass. However, it would be much harder to turn the optimization off when it is not
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* necessary, making the construction potentially slower in those cases.
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* - Doing optimizations directly would also make code more complex, because it mixes the logic
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* that generates the procedure from some other data with optimization decisions.
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* - Having a separate pass allows us to use it in different places when necessary.
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* - Having a separate pass allows us to enable and disable it easily to better understand its
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* impact on performance.
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*/
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#include "FN_multi_function_procedure.hh"
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namespace blender::fn::multi_function::procedure_optimization {
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/**
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* When generating a procedure, destruct instructions (#DestructInstruction) have to be inserted
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* for all variables that are not outputs. Often the simplest approach is to add these instructions
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* at the very end. However, when the procedure is executed this is not optimal, because many more
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* variables are initialized at the same time than necessary. This inhibits the reuse of memory
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* buffers which decreases performance and increases memory use.
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*
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* This optimization pass moves destruct instructions up in the procedure. The goal is to destruct
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* each variable right after its last use.
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*
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* For simplicity, and because this is the most common use case, this optimization currently only
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* works on a single chain of instructions. Destruct instructions are not moved across branches.
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*
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* \param procedure: The procedure that should be optimized.
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* \param block_end_instr: The instruction that points to the last instruction within a linear
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* chain of instructions. The algorithm moves instructions backward starting at this instruction.
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*/
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void move_destructs_up(Procedure &procedure, Instruction &block_end_instr);
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} // namespace blender::fn::multi_function::procedure_optimization
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