Implement optimize(size) and optimize(speed) attributes
This PR implements both `optimize(size)` and `optimize(speed)` attributes.
While the functionality itself works fine now, this PR is not yet complete: the code might be messy in places and, most importantly, the compiletest must be improved with functionality to run tests with custom optimization levels. Otherwise the new attribute cannot be tested properly. Oh, and not all of the RFC is implemented – attribute propagation is not implemented for example.
# TODO
* [x] Improve compiletest so that tests can be written;
* [x] Assign a proper error number (E9999 currently, no idea how to allocate a number properly);
* [ ] Perhaps reduce the duplication in LLVM attribute assignment code…
The new git submodule src/llvm-project is a monorepo replacing src/llvm
and src/tools/{clang,lld,lldb}. This also serves as a rebase for these
projects to the new 8.x branch from trunk.
The src/llvm-emscripten fork is unchanged for now.
Bump minimum required LLVM version to 6.0
Based on the discussion in #55842, while the overall position of Rust wrt LLVM continues to be contentious, there does seem to be a consensus that there is no need for continued support of LLVM 5. This PR bumps our version requirement to LLVM 6.0 and makes Travis run against that.
I hope that this is going to unblock #52694. If I understand correctly, while this issue still exists in LLVM 6, Ubuntu has backported the relevant patch.
r? @alexcrichton
If the Rust LLVM fork is used, enable the -mergefunc-use-aliases
flag, which will create aliases for merged functions, rather than
inserting a call from one to the other.
A number of codegen tests needed to be adjusted, because functions
that previously fell below the thunk limit are now being merged.
Merging is prevented either using -C no-prepopulate-passes, or by
making the functions non-identical.
I expect that this is going to break something, somewhere, because
it isn't able to deal with aliases properly, but we won't find out
until we try :)
This fixes#52651.
Update emscripten
This updates emscripten to 1.38.15, which is based on LLVM 6.0.1 and would allow us to drop code for handling LLVM 4.
The main issue I ran into is that exporting statics through `EXPORTED_FUNCTIONS` no longer works. As far as I understand exporting non-functions doesn't really make sense under emscripten anyway, so I've modified the symbol export code to not even try.
Closes#52323.
Support memcpy/memmove with differing src/dst alignment
If LLVM 7 is used, generate memcpy/memmove with differing src/dst alignment. I've added new FFI functions to construct these through the builder API, which is more convenient than dealing with differing intrinsic signatures depending on the LLVM version.
Fixes#49740.
If LLVM 7 is used, generate memcpy/memmove with differing
src/dst alignment. I've added new FFI functions to construct
these through the builder API, which is more convenient than
dealing with differing intrinsic signatures depending on the
LLVM version.
The DWARF generated for Rust enums was always somewhat unusual.
Rather than using DWARF constructs directly, it would emit magic field
names like "RUST$ENCODED$ENUM$0$Name" and "RUST$ENUM$DISR". Since
PR #45225, though, even this has not worked -- the ad hoc scheme was
not updated to handle the wider variety of niche-filling layout
optimizations now available.
This patch changes the generated DWARF to use the standard tags meant
for this purpose; namely, DW_TAG_variant and DW_TAG_variant_part.
The patch to implement this went in to LLVM 7. In order to work with
older versions of LLVM, and because LLVM doesn't do anything here for
PDB, the existing code is kept as a fallback mode.
Support for this DWARF is in the Rust lldb and in gdb 8.2.
Closes#32920Closes#32924Closes#52762Closes#53153
The issue of passing around SIMD types as values between functions has
seen [quite a lot] of [discussion], and although we thought [we fixed
it][quite a lot] it [wasn't]! This PR is a change to rustc to, again,
try to fix this issue.
The fundamental problem here remains the same, if a SIMD vector argument
is passed by-value in LLVM's function type, then if the caller and
callee disagree on target features a miscompile happens. We solve this
by never passing SIMD vectors by-value, but LLVM will still thwart us
with its argument promotion pass to promote by-ref SIMD arguments to
by-val SIMD arguments.
This commit is an attempt to thwart LLVM thwarting us. We, just before
codegen, will take yet another look at the LLVM module and demote any
by-value SIMD arguments we see. This is a very manual attempt by us to
ensure the codegen for a module keeps working, and it unfortunately is
likely producing suboptimal code, even in release mode. The saving grace
for this, in theory, is that if SIMD types are passed by-value across
a boundary in release mode it's pretty unlikely to be performance
sensitive (as it's already doing a load/store, and otherwise
perf-sensitive bits should be inlined).
The implementation here is basically a big wad of C++. It was largely
copied from LLVM's own argument promotion pass, only doing the reverse.
In local testing this...
Closes#50154Closes#52636Closes#54583Closes#55059
[quite a lot]: https://github.com/rust-lang/rust/pull/47743
[discussion]: https://github.com/rust-lang/rust/issues/44367
[wasn't]: https://github.com/rust-lang/rust/issues/50154
The issue of passing around SIMD types as values between functions has
seen [quite a lot] of [discussion], and although we thought [we fixed
it][quite a lot] it [wasn't]! This PR is a change to rustc to, again,
try to fix this issue.
The fundamental problem here remains the same, if a SIMD vector argument
is passed by-value in LLVM's function type, then if the caller and
callee disagree on target features a miscompile happens. We solve this
by never passing SIMD vectors by-value, but LLVM will still thwart us
with its argument promotion pass to promote by-ref SIMD arguments to
by-val SIMD arguments.
This commit is an attempt to thwart LLVM thwarting us. We, just before
codegen, will take yet another look at the LLVM module and demote any
by-value SIMD arguments we see. This is a very manual attempt by us to
ensure the codegen for a module keeps working, and it unfortunately is
likely producing suboptimal code, even in release mode. The saving grace
for this, in theory, is that if SIMD types are passed by-value across
a boundary in release mode it's pretty unlikely to be performance
sensitive (as it's already doing a load/store, and otherwise
perf-sensitive bits should be inlined).
The implementation here is basically a big wad of C++. It was largely
copied from LLVM's own argument promotion pass, only doing the reverse.
In local testing this...
Closes#50154Closes#52636Closes#54583Closes#55059
[quite a lot]: https://github.com/rust-lang/rust/pull/47743
[discussion]: https://github.com/rust-lang/rust/issues/44367
[wasn't]: https://github.com/rust-lang/rust/issues/50154
Disable the PLT where possible to improve performance
for indirect calls into shared libraries.
This optimization is enabled by default where possible.
- Add the `NonLazyBind` attribute to `rustllvm`:
This attribute informs LLVM to skip PLT calls in codegen.
- Disable PLT unconditionally:
Apply the `NonLazyBind` attribute on every function.
- Only enable no-plt when full relro is enabled:
Ensures we only enable it when we have linker support.
- Add `-Z plt` as a compiler option
codegen_llvm: check inline assembly constraints with LLVM
---%<---
Hey all,
As issue #54130 highlights, constraints are not checked and passing bad constraints to LLVM can crash it since a `Verify()` call is placed inside an assertion (see: `src/llvm/lib/IR/InlineAsm.cpp:39`).
As this is my first PR to the Rust compiler (woot! 🎉), there might be better ways of achieving this result. In particular, I am not too happy about generating an error in codegen; it would be much nicer if we did it earlier. However, @rkruppe [noted on IRC](https://botbot.me/mozilla/rustc/2018-09-25/?msg=104791581&page=1) that this should be fine for an unstable feature and a much better solution than the _status quo_, which is an ICE.
Thanks!
--->%---
LLVM provides a way of checking whether the constraints and the actual
inline assembly make sense. This commit introduces a check before
emitting code for the inline assembly. If LLVM rejects the inline
assembly (or its constraints), then the compiler emits an error E0668
("malformed inline assembly").
Fixes: #54130
Signed-off-by: Levente Kurusa \<lkurusa@acm.org\>
LLVM provides a way of checking whether the constraints and the actual
inline assembly make sense. This commit introduces a check before
emitting code for the inline assembly. If LLVM rejects the inline
assembly (or its constraints), then the compiler emits an error E0668
("malformed inline assembly").
Signed-off-by: Levente Kurusa <lkurusa@acm.org>
Enable ThinLTO with incremental compilation.
This is an updated version of #52309. This PR allows `rustc` to use (local) ThinLTO and incremental compilation at the same time. In theory this should allow for getting compile-time improvements for small changes while keeping the runtime performance of the generated code roughly the same as when compiling non-incrementally.
The difference to #52309 is that this version also caches the pre-LTO version of LLVM bitcode. This allows for another layer of caching:
1. if the module itself has changed, we have to re-codegen and re-optimize.
2. if the module itself has not changed, but a module it imported from during ThinLTO has, we don't need to re-codegen and don't need to re-run the first optimization phase. Only the second (i.e. ThinLTO-) optimization phase is re-run.
3. if neither the module itself nor any of its imports have changed then we can re-use the final, post-ThinLTO version of the module. (We might have to load its pre-ThinLTO version though so it's available for other modules to import from)
This commit updates the LLVM submodule to the current trunk of LLVM itself. This
brings a few notable improvements for the wasm target:
* Support for wasm atomic instructions is greatly improved
* Renamed memory wasm intrinsics are fully supported
* LLD has fixed a quadratic execution bug with large numbers of relocations in
wasm files.
The compiler-rt submodule has been updated in tandem as well.
This fixes a regression from #53031 where specifying `-C target-cpu=native` is
printing a lot of warnings from LLVM about `native` being an unknown CPU. It
turns out that `native` is indeed an unknown CPU and we have to perform a
mapping to an actual CPU name, but this mapping is only performed in one
location rather than all locations we inform LLVM about the target CPU.
This commit centralizes the mapping of `native` to LLVM's value of the native
CPU, ensuring that all locations we inform LLVM about the `target-cpu` it's
never `native`.
Closes#53322
In some profiling on OSX I saw the `write` syscall as quite high up on
the profiling graph, which is definitely not good! It looks like we're
setting the output stream of an object file as directly to a file
descriptor which means that we run the risk of doing lots of little
writes rather than a few large writes.
This commit fixes this issue by adding a buffered stream on the output,
causing the `write` syscall to disappear from the profiles on OSX.
rustc: Handle linker diagnostics from LLVM
Previously linker diagnostic were being hidden when two modules were linked
together but failed to link. This commit fixes the situation by ensuring that we
have a diagnostic handler installed and also adds support for handling linker
diagnostics.
Fix -Wpessimizing-move warnings in rustllvm/PassWrapper
These are producing warnings when building rustc (`warning: moving a local object in a return statement prevents copy elision [-Wpessimizing-move]`).
Previously linker diagnostic were being hidden when two modules were linked
together but failed to link. This commit fixes the situation by ensuring that we
have a diagnostic handler installed and also adds support for handling linker
diagnostics.
