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Support integrate 3rd-party toolchains into wamrc (#1237)

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Support integrating 3rd-party toolchain llc compiler or asm compiler
into wamrc by setting environment variable WAMRC_LLC_COMPILER
or WAMRC_ASM_COMPILER, wamrc will use these tools to generate
object file from LLVM IR firstly, and then refactor the object file into
aot file.
This commit is contained in:
Xu Jun
2022-06-20 13:13:41 +08:00
committed by GitHub
parent bc6eda2803
commit 53b775aa4b
8 changed files with 241 additions and 1 deletions
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doc/build_wasm_app.md
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@ -330,6 +330,36 @@ Examples: wamrc -o test.aot test.wasm
wamrc --target=i386 --format=object -o test.o test.wasm
```
## AoT compilation with 3rd-party toolchains
`wamrc` uses LLVM to compile wasm bytecode to AoT file, this works for most of the architectures, but there may be circumstances where you want to use 3rd-party toolchains to take over some steps of the compilation pipeline, e.g.
1. The upstream LLVM doesn't support generating object file for your CPU architecture (such as ARC), then we may need some other assembler to do such things.
2. You may get some other LLVM-based toolchains which may have better optimizations for the specific target, then you may want your toolchain to take over all optimization steps.
`wamrc` provides two environment variables to achieve these:
- `WAMRC_LLC_COMPILER`
When specified, `wamrc` will emit the optimized LLVM-IR (.bc) to a file, and invoke `$WAMRC_LLC_COMPILER` with ` -c -O3 ` to generate the object file.
Optionally, you can use environment variable `WAMRC_LLC_FLAGS` to overwrite the default flags.
- `WAMRC_ASM_COMPILER`
When specified, `wamrc` will emit the text based assembly file (.s), and invoke `$WAMRC_ASM_COMPILER` with ` -c -O3 ` to generate the object file.
Optionally, you can use environment variable `WAMRC_ASM_FLAGS` to overwrite the default flags.
### Usage example
``` bash
WAMRC_LLC_COMPILER=<path/to/your/compiler/driver> ./wamrc -o test.aot test.wasm
```
> Note: `wamrc` will verify whether the specified file exists and executable. If verification failed, `wamrc` will report a warning and fallback to normal pipeline. Since the verification is based on file, you **must specify the absolute path to the binary** even if it's in `$PATH`
> Note: `WAMRC_LLC_COMPILER` has higher priority than `WAMRC_ASM_COMPILER`, if `WAMRC_LLC_COMPILER` is set and verified, then `WAMRC_ASM_COMPILER` will be ignored.
> Note: the `LLC` and `ASM` in the env name just means this compiler will be used to compile the `LLVM IR file`/`assembly file` to object file, usually passing the compiler driver is the simplest way. (e.g. for LLVM toolchain, you don't need to pass `/usr/bin/llc`, using `/usr/bin/clang` is OK)
Run WASM app in WAMR mini product build
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