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<title>Code motion</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Code motion</span></span>

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<p>In <a href="Computer_science" title="Computer science">computer science</a>, <b>code motion</b>, which includes code hoisting, code sinking, loop-invariant code motion, and code factoring, is a blanket term for any process that moves code within a program. This is typically done for performance and size benefits, and it is a common <a href="Optimization" class="mw-redirect" title="Optimization">optimization</a> performed in most <a href="Optimizing_compilers" class="mw-redirect" title="Optimizing compilers">optimizing compilers</a>.

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<p>Code motion has a variety of uses and benefits, many of which overlap each other in their implementation.

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<div class="mw-heading mw-heading3"><h3 id="Removing_unused/useless_operations">Removing unused/useless operations</h3></div>

<p><b>Code Sinking</b>, also known as <b>lazy code motion</b>, is a term for a technique that reduces wasted instructions by moving instructions to branches in which they are used:<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> If an operation is executed before a branch, and only one of the branch paths use the result of that operation, then code sinking entails moving that operation into the branch where it will be used.

</p><p>This technique is a form of <a href="Dead_code_elimination" class="mw-redirect" title="Dead code elimination">dead code elimination</a> in the sense that it removes code when its results are discarded or unused, but in contrast to dead code elimination, it can remove pointless instructions even if there is a possible use of that instruction’s results in an execution code path.

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<div class="mw-heading mw-heading3"><h3 id="Reducing_the_size_of_the_program">Reducing the size of the program</h3></div>

<p><b>Code Factoring</b> is a term for a size-optimization technique that merges common dependencies in branches into the branch above it.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Just like <a href="Integer_factorization" title="Integer factorization">factorizing integers</a> decomposes a number into its smallest possible forms (as factors), code factorization transforms the code into the smallest possible form, by merging common "factors" until no duplicates remain.

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<div class="mw-heading mw-heading3"><h3 id="Reducing_dependency_stalls">Reducing dependency stalls</h3></div>

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</style><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Instruction_scheduling" title="Instruction scheduling">Instruction scheduling</a></div>

<p><b>Global code motion</b>, <b>local code motion</b>, <b>code scheduling</b>, <b><a href="Instruction_scheduling" title="Instruction scheduling">Instruction scheduling</a></b> and <b>code hoisting/sinking</b> are all terms for a technique where instructions are rearranged (or "scheduled") to improve the efficiency of <a href="Out-of-order_execution" title="Out-of-order execution">execution</a> within the CPU.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Modern <a href="CPU" class="mw-redirect" title="CPU">CPUs</a> are able to schedule five or more instructions per clock cycle. However, a CPU cannot schedule an instruction that relies on data from a currently (or not yet executed) instruction. Compilers will interleave dependencies in a manner that maximizes the amount of instructions a CPU can process at any point in time.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>

</p><p>On the defunct <a href="Itanium" title="Itanium">Intel Itanium</a> architecture, the <a href="Branch_predictor" title="Branch predictor">branch predict</a> (BRP) instruction is manually hoisted above branches by the compiler to enable the branch to be immediately taken by the CPU. Itanium relies on additional code scheduling from the CPU to maximize efficiency in the processor.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Loop-invariant_code_motion">Loop-invariant code motion</h2></div>

<div role="note" class="hatnote navigation-not-searchable">Main article: <a href="Loop-invariant_code_motion" title="Loop-invariant code motion">Loop-invariant code motion</a></div>

<p>Loop-invariant code motion is the process of moving loop-invariant code to a position outside the loop, which may reduce the execution time of the loop by preventing some computations from being done twice for the same result.

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<div class="mw-heading mw-heading2"><h2 id="Compiler_examples">Compiler examples</h2></div>

<p><a href="LLVM" title="LLVM">LLVM</a> has a sinking pass in its single static assignment form. LLVM 15.0 will not sink an operation if any of its code paths include a store instruction, or if it may throw an error.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Additionally, LLVM will not sink an instruction <i>into</i> a loop.

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<p>The <a href="GNU_Compiler_Collection" title="GNU Compiler Collection">GNU Compiler Collection</a> implements code motion under the name "code factoring", with the purpose of reducing the size of a compiled program.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> GCC will move any code upwards or downwards if it "[does not] invalidate any existing dependences nor introduce new ones".<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading3"><h3 id="LuaJIT">LuaJIT</h3></div>

<p><a href="LuaJIT" title="LuaJIT">LuaJIT</a> uses code sinking under the name "Allocation sinking", to reduce the amount of time compiled code spends allocating and collecting temporary objects within a loop.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> Allocation sinking moves allocations to execution paths where the allocated object may escape the executing code, and will thus require <a href="Heap_allocation" class="mw-redirect" title="Heap allocation">heap allocation</a>. All removed allocations are filled in with load-to-store forwarding over their fields.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup>

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<ul><li><a href="Loop-invariant_code_motion" title="Loop-invariant code motion">Loop-invariant code motion</a></li>

<li><a href="Instruction_scheduling" title="Instruction scheduling">Instruction scheduling</a></li>

<li><a href="Dependency_graph" title="Dependency graph">Dependency graph</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite id="CITEREFCraftOffut1994" class="citation journal cs1">Craft, Michael; Offut, Jefferson (1994). <span class="id-lock-subscription" title="Paid subscription required"><a rel="nofollow" class="external text" href="https://onlinelibrary.wiley.com/doi/10.1002/stvr.4370040303">"Using compiler optimization techniques to detect equivalent mutants"</a></span>. <i>Software Testing, Verification & Reliability</i>. <b>4</b> (3): <span class="nowrap">131–</span>154. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fstvr.4370040303">10.1002/stvr.4370040303</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:35717348">35717348</a><span class="reference-accessdate">. Retrieved <span class="nowrap">25 February</span> 2022</span>.</cite></span>

</li>

<li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"> Lóki, Gábor, et al. "Code factoring in GCC." Proceedings of the 2004 GCC Developers’ Summit. 2004.</span>

</li>

<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text">Fasse, Justus, et al. Code Transformations to Increase Prepass Scheduling Opportunities in CompCert. Diss. Master Thesis of Science. Université Grenoble Alpes. <a rel="nofollow" class="external free" href="https://www-verimag">https://www-verimag</a>. imag. fr/~ boulme/CPP_2022/FASSE-Justus-MSc-Thesis_2021. pdf, 2021.</span>

</li>

<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><cite id="CITEREFGupta1998" class="citation book cs1">Gupta, Rajiv (1998). "A code motion framework for global instruction scheduling". <i>Compiler Construction</i>. Lecture Notes in Computer Science. Vol. 1383. pp. <span class="nowrap">219–</span>233. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1007%2FBFb0026434">10.1007/BFb0026434</a></span>. <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>978-3-540-64304-3</bdi>.</cite></span>

</li>

<li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"> Chang, Pohua P., et al. "The importance of prepass code scheduling for superscalar and superpipelined processors." IEEE Transactions on Computers 44.3 (1995): 353-370. </span>

</li>

<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite id="CITEREFSharangpaniArora2000" class="citation journal cs1">Sharangpani, H.; Arora, H. (September 2000). <span class="id-lock-subscription" title="Paid subscription required"><a rel="nofollow" class="external text" href="https://ieeexplore.ieee.org/document/877948">"Itanium processor microarchitecture"</a></span>. <i>IEEE Micro</i>. <b>20</b> (5): <span class="nowrap">24–</span>43. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2F40.877948">10.1109/40.877948</a>. <a href="ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1937-4143">1937-4143</a>.</cite></span>

</li>

<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://llvm.org/doxygen/Sink_8cpp_source.html">"LLVM: lib/Transforms/Scalar/Sink.cpp Source File"</a>. <i>llvm.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 February</span> 2022</span>.</cite></span>

</li>

<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://gcc.gnu.org/projects/cfo.html">"Code Factoring Optimizations - GNU Project"</a>. <i>gcc.gnu.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 February</span> 2022</span>.</cite></span>

</li>

<li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://gcc.gnu.org/pub/gcc/summit/2004/Code%20Factoring.pdf">"GCC Developer's Summit 2004 - Code Factoring.pdf"</a> <span class="cs1-format">(PDF)</span>. <i>gnu.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 February</span> 2022</span>.</cite></span>

</li>

<li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.freelists.org/post/luajit/Allocation-sinking-in-git-HEAD">"Allocation sinking in git HEAD - luajit - FreeLists"</a>. <i>www.freelists.org</i><span class="reference-accessdate">. Retrieved <span class="nowrap">25 February</span> 2022</span>.</cite></span>

</li>

<li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://wiki.luajit.org/Allocation-Sinking-Optimization">"Allocation Sinking Optimization"</a>. <i>wiki.luajit.org</i>.</cite></span>

</li>

</ol></div></div>

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</style><div id="Compiler_optimizations253" style="font-size:114%;margin:0 4em"><a href="Optimizing_compiler" title="Optimizing compiler">Compiler optimizations</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Basic block</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Peephole_optimization" title="Peephole optimization">Peephole optimization</a></li>

<li><a href="Local_value_numbering" class="mw-redirect" title="Local value numbering">Local value numbering</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Loop_optimization" title="Loop optimization">Loop</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Automatic_parallelization" title="Automatic parallelization">Automatic parallelization</a></li>

<li><a href="Automatic_vectorization" title="Automatic vectorization">Automatic vectorization</a></li>

<li><a href="Induction_variable" title="Induction variable">Induction variable</a></li>

<li><a href="Loop_fusion" class="mw-redirect" title="Loop fusion">Loop fusion</a></li>

<li><a href="Loop-invariant_code_motion" title="Loop-invariant code motion">Loop-invariant code motion</a></li>

<li><a href="Loop_inversion" title="Loop inversion">Loop inversion</a></li>

<li><a href="Loop_interchange" title="Loop interchange">Loop interchange</a></li>

<li><a href="Loop_nest_optimization" title="Loop nest optimization">Loop nest optimization</a></li>

<li><a href="Loop_splitting" title="Loop splitting">Loop splitting</a></li>

<li><a href="Loop_unrolling" title="Loop unrolling">Loop unrolling</a></li>

<li><a href="Loop_unswitching" title="Loop unswitching">Loop unswitching</a></li>

<li><a href="Software_pipelining" title="Software pipelining">Software pipelining</a></li>

<li><a href="Strength_reduction" title="Strength reduction">Strength reduction</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Data-flow_analysis" title="Data-flow analysis">Data-flow<br>analysis</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Available_expression" title="Available expression">Available expression</a></li>

<li><a href="Common_subexpression_elimination" title="Common subexpression elimination">Common subexpression elimination</a></li>

<li><a href="Constant_folding" title="Constant folding">Constant folding</a></li>

<li><a href="Dead_store" title="Dead store">Dead store</a> elimination</li>

<li><a href="Induction_variable_recognition_and_elimination" class="mw-redirect" title="Induction variable recognition and elimination">Induction variable recognition and elimination</a></li>

<li><a href="Live-variable_analysis" title="Live-variable analysis">Live-variable analysis</a></li>

<li><a href="Upwards_exposed_uses" title="Upwards exposed uses">Upwards exposed uses</a></li>

<li><a href="Use-define_chain" title="Use-define chain">Use-define chain</a></li>

<li><a href="Reaching_definition" title="Reaching definition">Reaching definitions</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Static_single-assignment_form" title="Static single-assignment form">SSA</a>-based</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Global_value_numbering" class="mw-redirect" title="Global value numbering">Global value numbering</a></li>

<li><a href="Sparse_conditional_constant_propagation" title="Sparse conditional constant propagation">Sparse conditional constant propagation</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Code_generation_(compiler)" title="Code generation (compiler)">Code generation</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Instruction_scheduling" title="Instruction scheduling">Instruction scheduling</a></li>

<li><a href="Instruction_selection" title="Instruction selection">Instruction selection</a></li>

<li><a href="Register_allocation" title="Register allocation">Register allocation</a></li>

<li><a href="Rematerialization" title="Rematerialization">Rematerialization</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Functional</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Deforestation_(computer_science)" title="Deforestation (computer science)">Deforestation</a></li>

<li><a href="Tail_call" title="Tail call">Tail-call elimination</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Global</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Interprocedural_optimization" title="Interprocedural optimization">Interprocedural optimization</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Bounds-checking_elimination" title="Bounds-checking elimination">Bounds-checking elimination</a></li>

<li><a href="Compile-time_function_execution" title="Compile-time function execution">Compile-time function execution</a></li>

<li><a href="Dead-code_elimination" title="Dead-code elimination">Dead-code elimination</a></li>

<li><a href="Expression_templates" title="Expression templates">Expression templates</a></li>

<li><a href="Inline_expansion" title="Inline expansion">Inline expansion</a></li>

<li><a href="Jump_threading" title="Jump threading">Jump threading</a></li>

<li><a href="Partial_evaluation" title="Partial evaluation">Partial evaluation</a></li>

<li><a href="Profile-guided_optimization" title="Profile-guided optimization">Profile-guided optimization</a></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Static analysis</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Alias_analysis" title="Alias analysis">Alias analysis</a></li>

<li><a href="Array-access_analysis" title="Array-access analysis">Array-access analysis</a></li>

<li><a href="Control-flow_analysis" title="Control-flow analysis">Control-flow analysis</a></li>

<li><a href="Data-flow_analysis" title="Data-flow analysis">Data-flow analysis</a></li>

<li><a href="Dependence_analysis" title="Dependence analysis">Dependence analysis</a></li>

<li><a href="Escape_analysis" title="Escape analysis">Escape analysis</a></li>

<li><a href="Pointer_analysis" title="Pointer analysis">Pointer analysis</a></li>

<li><a href="Shape_analysis_(program_analysis)" title="Shape analysis (program analysis)">Shape analysis</a></li>

<li><a href="Value_range_analysis" title="Value range analysis">Value range analysis</a></li></ul>

</div></td></tr></tbody></table></div></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2025-07-04" href="https://en.wikipedia.org/wiki/?title=Code_motion&oldid=1298761117">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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