path: root/config.toml.example
diff options
authorAlex Crichton <>2018-01-24 08:22:34 -0800
committerAlex Crichton <>2018-01-28 18:32:45 -0800
commitc6daea7c9a7d4be88e1ae8d54d992937fcfe24fa (patch)
tree29d8d7e69c49ae4e9930c3568ebccb8b840cfde1 /config.toml.example
parentAuto merge of #47663 - malbarbo:mips-crt-static, r=alexcrichton (diff)
rustc: Split Emscripten to a separate codegen backend
This commit introduces a separately compiled backend for Emscripten, avoiding compiling the `JSBackend` target in the main LLVM codegen backend. This builds on the foundation provided by #47671 to create a new codegen backend dedicated solely to Emscripten, removing the `JSBackend` of the main codegen backend in the process. A new field was added to each target for this commit which specifies the backend to use for translation, the default being `llvm` which is the main backend that we use. The Emscripten targets specify an `emscripten` backend instead of the main `llvm` one. There's a whole bunch of consequences of this change, but I'll try to enumerate them here: * A *second* LLVM submodule was added in this commit. The main LLVM submodule will soon start to drift from the Emscripten submodule, but currently they're both at the same revision. * Logic was added to rustbuild to *not* build the Emscripten backend by default. This is gated behind a `--enable-emscripten` flag to the configure script. By default users should neither check out the emscripten submodule nor compile it. * The `` script was updated to fetch the Emscripten submodule from GitHub the same way we do the main LLVM submodule (a tarball fetch). * The Emscripten backend, turned off by default, is still turned on for a number of targets on CI. We'll only be shipping an Emscripten backend with Tier 1 platforms, though. All cross-compiled platforms will not be receiving an Emscripten backend yet. This commit means that when you download the `rustc` package in Rustup for Tier 1 platforms you'll be receiving two trans backends, one for Emscripten and one that's the general LLVM backend. If you never compile for Emscripten you'll never use the Emscripten backend, so we may update this one day to only download the Emscripten backend when you add the Emscripten target. For now though it's just an extra 10MB gzip'd. Closes #46819
Diffstat (limited to 'config.toml.example')
1 files changed, 7 insertions, 0 deletions
diff --git a/config.toml.example b/config.toml.example
index 18c1f160c0..1d60d8c949 100644
--- a/config.toml.example
+++ b/config.toml.example
@@ -305,6 +305,13 @@
305# result (broken, compiling, testing) into this JSON file. 305# result (broken, compiling, testing) into this JSON file.
306#save-toolstates = "/path/to/toolstates.json" 306#save-toolstates = "/path/to/toolstates.json"
307 307
308# This is an array of the codegen backends that will be compiled for the rustc
309# that's being compiled. The default is to only build the LLVM codegen backend,
310# but you can also optionally enable the "emscripten" backend for asm.js or
311# make this an empty array (but that probably won't get too far in the
312# bootstrap)
313#codegen-backends = ["llvm"]
308# ============================================================================= 315# =============================================================================
309# Options for specific targets 316# Options for specific targets
310# 317#