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notes/Copy-and-Patch Compilation.md
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@ -5,20 +5,20 @@ Copy and patch is a novel compilation technique introduced in the above paper th
They provide two example use cases, a compiler for a C-like language, and a WebAssembly compiler, and show promising results for both startup time and execution performance. They provide two example use cases, a compiler for a C-like language, and a WebAssembly compiler, and show promising results for both startup time and execution performance.
(Bottom of Page 2): (Bottom of Page 2):
> Our compiler achieves both lower startup delay and better execution performance than > Our compiler achieves both lower startup delay and better execution performance than prior baseline compilers. Figure 2 shows the performance of six WebAssembly compilers on the PolyBenchC benchmark, normalized to our performance. Our compiler has 6.5× lower startup delay than Liftoff, while generating on average 63% better-performing code.
prior baseline compilers. Figure 2 shows the performance of six WebAssembly compilers on the
PolyBenchC benchmark, normalized to our performance. Our compiler
has 6.5× lower startup delay than Liftoff, while generating on average 63% better-performing code.
Their C implementation is feature complete, and even includes some functionality like C++ (classes, destructor semantics). Their C-like implementation is feature complete, and even includes some functionality like C++ (classes, destructor semantics).
One proposed use case of copy-and-patch compilation in the paper is as an SQL query engine, noting that they believe they have built the first baseline compiler for an SQL query engine. One proposed use case of copy-and-patch compilation in the paper is as an SQL query engine, noting that they believe they have built the first baseline compiler for an SQL query engine. Using the above C-like DSL, they built a simple SQL query engine, and note impressive performance gains over previous optimizing compilers or interpreters:
(Halfway through Page 3):
> The compilation time of our compiler is so low that it is less than the time it takes to construct the AST of the program. Compared with interpreters, both have negligible startup delay (since constructing ASTs takes longer), but our execution performance is an order of magnitude faster. Compared with LLVM -O0, our implementation compiles two orders of magnitude faster and generates code that performs on average 14% better. Therefore, we conclude that copy-and-patch renders both interpreters and LLVM -O0 compilation obsolete in this use case.
# Terminology # Terminology
| Phrase | Definition | | Phrase | Definition |
| ------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------- | | ------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| Stencil | A binary implementation that has holes where missing values must be inserted during codegen. | | Stencil | A binary implementation that has holes where missing values must be inserted during codegen. |
| Full Compiler | A compiler that compiles from a high level language to machine code | | Full Compiler | A compiler that compiles from a high level language to machine code |
| Bytecode Assembler | An assembler that converts low level bytecode to machine code. | | Bytecode Assembler | An assembler that converts low level bytecode to machine code. |
| Baseline compiler | In tiered compilation, a baseline compiler is the first compiler. It's meant to be the fastest, with the lowest priority on generating performant code. | | Baseline compiler | In tiered compilation, a baseline compiler is the first compiler. It's meant to be the fastest, with the lowest priority on generating performant code. |
| Pareto Frontier | In multi-objective optimization, the pareto frontier is the set of solutions that are best | | Pareto Frontier | In multi-objective optimization, the pareto frontier is the set of solutions that represent "ideal" tradeoffs between one and the other, rejecting suboptimal solutions. |