Like most compilers, TinyGo is a compiler built as a pipeline of transformations
that each translate an input to a simpler output version (also called lowering).
However, most of these part are not in TinyGo itself. The frontend is mostly
implemented by external Go libraries, and most optimizations and code generation
is implemented by LLVM.
This is roughly the pipeline for TinyGo:
- Lexing, parsing, and typechecking is done by packages in the
standard library and in the
construction (a very important step) is done by the
- The Go SSA is then transformed into LLVM IR by the
Both forms are SSA, but because Go SSA is higher level and contains
Go-specific constructs (like interfaces and goroutines) this is non-trivial.
However, the vast majority of the work is simply lowering the available Go
SSA into LLVM IR, possibly calling some runtime library intrinsics in the
process (for example, operations on maps).
- Go does a lot of initialization at runtime, which is really bad for
code size. This includes all global variables: they are all initialized at
runtime, not at compile time like C. So TinyGo
interprets these functions at compile time
as far as it is able to.
- The resulting IR is then first optimized by a mixture of handpicked LLVM
optimization passes, TinyGo-specific
optimizations (escape analysis,
byte optimizations, etc.)
and custom lowering. For example, this is the time when interfaces are
lowered to their final form to benefit from the optimizations already done
until that point.
- This LLVM IR is then optimized by the LLVM optimizer, which has a large
array of standard optimization passes.
This is the standard optimization pipeline as is also used by Clang.
- After all optimizations have run, a few fixups are needed for AVR for
globals, because AVR has separate address spaces for flash and RAM. This is
implemented by the compiler package.
- Finally, the resulting machine code is emitted by LLVM to an object file.
This is just the compiler. TinyGo can also automatically link the file and flash
it to a device, if needed.