778b631ff0
rustc: Update wasm32 support for LLVM 9
This commit brings in a number of minor updates for rustc's support for
the wasm target which has changed in the LLVM 9 update. Notable updates
include:
* The compiler now no longer manually inserts the `producers` section,
instead relying on LLVM to do so. LLVM uses the `llvm.ident` metadata
for the `processed-by` directive (which is now emitted on the wasm
target in this PR) and it uses debuginfo to figure out what `language`
to put in the `producers` section.
* Threaded WebAssembly code now requires different flags to be passed
with LLD. In LLD we now pass:
* `--shared-memory` - required since objects are compiled with
atomics. This also means that the generated memory will be marked as
`shared`.
* `--max-memory=1GB` - required with the `--shared-memory` argument
since shared memories in WebAssembly must have a maximum size. The
1GB number is intended to be a conservative estimate for rustc, but
it should be overridable with `-C link-arg` if necessary.
* `--passive-segments` - this has become the default for multithreaded
memory, but when compiling a threaded module all data segments need
to be marked as passive to ensure they don't re-initialize memory
for each thread. This will also cause LLD to emit a synthetic
function to initialize memory which users will have to arrange to
call.
* The `__heap_base` and `__data_end` globals are explicitly exported
since they're now hidden by default due to the `--export` flags we
pass to LLD.
|
||
|---|---|---|
| .. | ||
| back | ||
| debuginfo | ||
| llvm | ||
| abi.rs | ||
| allocator.rs | ||
| asm.rs | ||
| attributes.rs | ||
| base.rs | ||
| build.rs | ||
| builder.rs | ||
| callee.rs | ||
| Cargo.toml | ||
| common.rs | ||
| consts.rs | ||
| context.rs | ||
| declare.rs | ||
| error_codes.rs | ||
| intrinsic.rs | ||
| lib.rs | ||
| llvm_util.rs | ||
| metadata.rs | ||
| mono_item.rs | ||
| README.md | ||
| type_.rs | ||
| type_of.rs | ||
| va_arg.rs | ||
| value.rs | ||
The codegen crate contains the code to convert from MIR into LLVM IR,
and then from LLVM IR into machine code. In general it contains code
that runs towards the end of the compilation process.
For more information about how codegen works, see the rustc guide.