rustc: Update wasm32 support for LLVM 9 #62809
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(rust_highfive has picked a reviewer for you, use r? to override) |
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cc @nikic |
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I've updated this as well with the necessary support to configure |
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| } else { | ||
| // stubbed out because no functions actually access these intrinsics | ||
| // unless atomics are enabled | ||
| MY_ID |
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What is the reason for using a compare_exchange loop here, rather than an atomic increment (something like MY_ID = NEXT_ID.fetch_add(1, SeqCst))? Is this not supported by wasm?
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While perhaps slightly overzealous, the thinking here is that if the counter everything should deterministically panic, as opposed to only one thread deterministically panicking but others continuing.
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I see. Maybe this is a nice opportunity to use the unstable fetch_update API, something like:
MY_ID = match NEXT_ID.fetch_update(|cur| cur.overflowing_add(1), SeqCst, SeqCst) {
Some(id) => id + 1,
Err(_) => crate::arch::wasm32::unreachable(),
}
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Oh good point! I think I'd prefer to avoid picking up an unstable feature for this since it's relatively minor, but I refactored a bit with your suggestion to use checked arithmetic which I think is better than what was there already!
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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.
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Sorry to bother y'all again, but I'm not sure who's best to review this? @rust-lang/compiler would y'all be ok helping me find a reviewer for this? |
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r? @nikic I'll review a bit later today... |
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| } else { | ||
| // stubbed out because no functions actually access these intrinsics | ||
| // unless atomics are enabled | ||
| MY_ID |
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I see. Maybe this is a nice opportunity to use the unstable fetch_update API, something like:
MY_ID = match NEXT_ID.fetch_update(|cur| cur.overflowing_add(1), SeqCst, SeqCst) {
Some(id) => id + 1,
Err(_) => crate::arch::wasm32::unreachable(),
}
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This commit moves `thread_local!` on WebAssembly targets to using the `#[thread_local]` attribute in LLVM. This was recently implemented upstream and is [in the process of being documented][dox]. This change only takes affect if modules are compiled with `+atomics` which is currently unstable and a pretty esoteric method of compiling wasm artifacts. This "new power" of the wasm toolchain means that the old `wasm-bindgen-threads` feature of the standard library can be removed since it should now be possible to create a fully functioning threaded wasm module without intrusively dealing with libstd symbols or intrinsics. Yay! [dox]: WebAssembly/tool-conventions#116
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@bors: r=nikic |
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📌 Commit dc50a63 has been approved by |
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The job Click to expand the log.I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact |
Centril
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Jul 28, 2019
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.
bors
added a commit
that referenced
this pull request
Jul 28, 2019
Rollup of 4 pull requests Successful merges: - #62550 (Implement RFC 2707 + Parser recovery for range patterns) - #62759 (Actually add rustc-guide to toolstate, don't fail builds for the guide) - #62809 (rustc: Update wasm32 support for LLVM 9) - #62974 (bump crossbeam-epoch dependency) Failed merges: r? @ghost
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⌛ Testing commit dc50a63 with merge e14bb100ce50095b35791513814b3cbdd10ea862... |
Centril
added a commit
to Centril/rust
that referenced
this pull request
Jul 29, 2019
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.
|
@bors retry rolled up. |
bors
added a commit
that referenced
this pull request
Jul 29, 2019
Rollup of 6 pull requests Successful merges: - #62809 (rustc: Update wasm32 support for LLVM 9) - #63055 (Various cleanups to save analysis) - #63076 (Miri: fix determining size of an "extra function" allocation) - #63077 (cleanup: Remove some language features related to built-in macros) - #63086 (Ignore test cases that are not supported by vxWorks) - #63092 (Update `impl Trait` gate issues) Failed merges: r? @ghost
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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
producerssection,instead relying on LLVM to do so. LLVM uses the
llvm.identmetadatafor the
processed-bydirective (which is now emitted on the wasmtarget in this PR) and it uses debuginfo to figure out what
languageto put in the
producerssection.Threaded WebAssembly code now requires different flags to be passed
with LLD. In LLD we now pass:
--shared-memory- required since objects are compiled withatomics. This also means that the generated memory will be marked as
shared.--max-memory=1GB- required with the--shared-memoryargumentsince 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-argif necessary.--passive-segments- this has become the default for multithreadedmemory, 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.
__heap_baseand__data_endglobals are explicitly exportedsince they're now hidden by default due to the
--exportflags wepass to LLD.