This commit builds on #65501 continue to simplify the build system and
compiler now that we no longer have multiple LLVM backends to ship by
default. Here this switches the compiler back to what it once was long
long ago, which is linking LLVM directly to the compiler rather than
dynamically loading it at runtime. The `codegen-backends` directory of
the sysroot no longer exists and all relevant support in the build
system is removed. Note that `rustc` still supports a dynamically loaded
codegen backend as it did previously, it just no longer supports
dynamically loaded codegen backends in its own sysroot.
Additionally as part of this the `librustc_codegen_llvm` crate now once
again explicitly depends on all of its crates instead of implicitly
loading them through the sysroot. This involved filling out its
`Cargo.toml` and deleting all the now-unnecessary `extern crate`
annotations in the header of the crate. (this in turn required adding a
number of imports for names of macros too).
The end results of this change are:
* Rustbuild's build process for the compiler as all the "oh don't forget
the codegen backend" checks can be easily removed.
* Building `rustc_codegen_llvm` is much simpler since it's simply
another compiler crate.
* Managing the dependencies of `rustc_codegen_llvm` is much simpler since
it's "just another `Cargo.toml` to edit"
* The build process should be a smidge faster because there's more
parallelism in the main rustc build step rather than splitting
`librustc_codegen_llvm` out to its own step.
* The compiler is expected to be slightly faster by default because the
codegen backend does not need to be dynamically loaded.
* Disabling LLVM as part of rustbuild is still supported, supporting
multiple codegen backends is still supported, and dynamic loading of a
codegen backend is still supported.
Migrate to LLVM{Get,Set}ValueName2
The deprecated `LLVM{Get,Set}ValueName` only work with NUL-terminated
strings, but the `2` variants use explicit lengths, which fits better
with Rust strings and slices. We now use these in new helper functions
`llvm::{get,set}_value_name` that convert to/from `&[u8]`.
Closes#64223.
r? @rkruppe
Use Module::print() instead of a PrintModulePass
llvm::Module has a print() method. It is unnecessary to create a pass just for the purpose of printing LLVM IR.
The deprecated `LLVM{Get,Set}ValueName` only work with NUL-terminated
strings, but the `2` variants use explicit lengths, which fits better
with Rust strings and slices. We now use these in new helper functions
`llvm::{get,set}_value_name` that convert to/from `&[u8]`.
For SGX, the relocation using the relocation table is done by
the code in rust/src/libstd/sys/sgx/abi/reloc.rs and this code
should not require relocation. Setting RelaxELFRelocations flag
if allows this to happen, hence adding a Target Option for it.
This addresses #65024, as it allows RISC-V target specification
files to set "llvm-abiname": "lp64d". In general, it is useful
for the programmer to be able to set this codegen parameter,
which other languages usually expose under a compiler argument
like "-mabi=<XYZ>".
Exception for specific cases like linting, additional passes should
be going into the module pass manager (even if they are function
passes). The separate function pass manager is only used for very
early optimization passes.
Rather than apparending passes to the MPM, use the OptimizerLast
and EnabledOnOptLevel0 pass manager builder extension hooks, which
allow adding passes directly before finalization (alias
canonicalization and name-anon-globals).
The main effect and purpose of this change is to add sanitizer
passes at the end of the pipeline, which is where they belong.
In LLVM 9 the address sanitizer can't be used as a pass in the
early function pass manager, because it has a dependence on a
module-level analysis pass.
Clean up handling of `-Z pgo-gen` commandline option.
This PR adapts the `-Z pgo-gen` flag to how Clang and GCC handle the corresponding `-fprofile-generate` flag. In particular, the flag now optionally takes a directory to place the profiling data in and allows to omit the argument (instead of having to pass an empty string).
Exclude profiler-generated symbols from MSVC __imp_-symbol workaround.
LLVM's profiling instrumentation adds a few symbols that are used by the profiler runtime. Since these show up as globals in the LLVM IR, the compiler generates `dllimport`-related `__imp_` stubs for them. This can lead to linker errors because the instrumentation symbols have weak linkage or are in a comdat section, but the `__imp_` stubs aren't.
Instead of trying to replicate the linkage/comdat setup for the stubs, this PR just excludes the profiler-related symbols from stub-generation since they aren't supposed to be referenced via `__declspec(dllimport)` anywhere anyway.
r? @alexcrichton
EDIT: I considered making this more general, i.e. inferring from the symbol name if it is a Rust symbol or not. But then I figured out that that would yield false negatives for `#[no_mangle]` et al, so I went with a blacklist approach.
I was trying to output LLVM IR directly to the console:
$ rustc hello.rs --emit=llvm-ir -o /dev/stdout
LLVM ERROR: IO failure on output stream: Bad file descriptor
Now `LLVMRustPrintModule` returns an error, and we print:
error: failed to write LLVM IR to /dev/stdout.hello.7rcbfp3g-cgu.0.rcgu.ll: Permission denied
... which is more informative.
Enable -mergefunc-use-aliases
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 in various ways now.
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.
r? @rkruppe
name-anon-globals should always be run at the very end of the pass
pipeline, as optimization passes (in particular mergefunc) may
introduce new anonymous globals.
I believe we did not run into this earlier because it requires the
rather specific combination of a) mergefunc merging two weak functions
b) compilation not using thinlto.
Alex Crichton
Yuki Okushi
bors
Josh Stone
Parth Sane
Victor Ding
Vadim Petrochenkov
Tomasz Miąsko
Robin Kruppe
David Wood
Gui Andrade
Mazdak Farrokhzad
memoryruins
Mark Rousskov
Michael Woerister
Nikita Popov
Jeremy Stucki
Eduard-Mihai Burtescu
Chandler Deng
bjorn3
Wesley Wiser
Simonas Kazlauskas
Taiki Endo
Alexander Regueiro
Corey Farwell
Denis Merigoux