MIR EndRegion Statements (was MIR dataflow for Borrows)
This PR adds an `EndRegion` statement to MIR (where the `EndRegion` statement is what terminates a borrow).
An earlier version of the PR implemented a dataflow analysis on borrow expressions, but I am now factoring that into a follow-up PR so that reviewing this one is easier. (And also because there are some revisions I want to make to that dataflow code, but I want this PR to get out of WIP status...)
This is a baby step towards MIR borrowck. I just want to get the review process going while I independently work on the remaining steps.
Introduce tidy lint to check for inconsistent tracking issues
This PR
* Refactors the collect_lib_features function to work in a
non-checking mode (no bad pointer needed, and list of
lang features).
* Introduces checking whether unstable/stable tags for a
given feature have inconsistent tracking issues, as in,
multiple tracking issues per feature.
* Fixes such inconsistencies throughout the codebase.
This commit
* Refactors the collect_lib_features function to work in a
non-checking mode (no bad pointer needed, and list of
lang features).
* Introduces checking whether unstable/stable tags for a
given feature have inconsistent tracking issues.
* Fixes such inconsistencies throughout the codebase.
Build instruction profiler runtime as part of compiler-rt
r? @alexcrichton
This is #38608 with some fixes.
Still missing:
- [x] testing with profiler enabled on some builders (on which ones? Should I add the option to some of the already existing configurations, or create a new configuration?);
- [x] enabling distribution (on which builders?);
- [x] documentation.
incr.comp.: Make DepNode `Copy` and valid across compilation sessions
This PR moves `DepNode` to a representation that does not need retracing and thus simplifies comparing dep-graphs from different compilation sessions. The code also gets a lot simpler in many places, since we don't need the generic parameter on `DepNode` anymore. See https://github.com/rust-lang/rust/issues/42294 for details.
~~NOTE: Only the last commit of this is new, the rest is already reviewed in https://github.com/rust-lang/rust/pull/42504.~~
This PR is almost done but there are some things I still want to do:
- [x] Add some module-level documentation to `dep_node.rs`, explaining especially what the `define_dep_nodes!()` macro is about.
- [x] Do another pass over the dep-graph loading logic. I suspect that we can get rid of building the `edges` map and also use arrays instead of hash maps in some places.
cc @rust-lang/compiler
r? @nikomatsakis
* Emit `EndRegion` for every code-extent for which we observe a
borrow. To do this, we needed to thread source info back through
to `fn in_scope`, which makes this commit a bit more painful than
one might have expected.
* There is `end_region` emission in `Builder::pop_scope` and in
`Builder::exit_scope`; the first handles falling out of a scope
normally, the second handles e.g. `break`.
* Remove `EndRegion` statements during the erase_regions mir
transformation.
* Preallocate the terminator block, and throw an `Unreachable` marker
on it from the outset. Then overwrite that Terminator as necessary
on demand.
* Instead of marking the scope as needs_cleanup after seeing a
borrow, just treat every scope in the chain as being part of the
diverge_block (after any *one* of them has separately signalled
that it needs cleanup, e.g. due to having a destructor to run).
* Allow for resume terminators to be patched when looking up drop flags.
(In particular, `MirPatch::new` has an explicit code path,
presumably previously unreachable, that patches up such resume
terminators.)
* Make `Scope` implement `Debug` trait.
* Expanded a stray comment: we do not emit StorageDead on diverging
paths, but that end behavior might not be desirable.
Get LLVM to stop generating dead assembly in next_power_of_two
It turns out that LLVM can turn `@llvm.ctlz.i64(_, true)` into `@llvm.ctlz.i64(_, false)` ([`ctlz`](http://llvm.org/docs/LangRef.html#llvm-ctlz-intrinsic)) where valuable, but never does the opposite. That leads to some silly assembly getting generated in certain cases.
A contrived-but-clear example https://is.gd/VAIKuC:
```rust
fn foo(x:u64) -> u32 {
if x == 0 { return !0; }
x.leading_zeros()
}
```
Generates
```asm
testq %rdi, %rdi
je .LBB0_1
je .LBB0_3 ; <-- wha?
bsrq %rdi, %rax
xorq $63, %rax
retq
.LBB0_1:
movl $-1, %eax
retq
.LBB0_3:
movl $64, %eax ; <-- dead
retq
```
I noticed this in `next_power_of_two`, which without this PR generates the following:
```asm
cmpq $2, %rcx
jae .LBB1_2
movl $1, %eax
retq
.LBB1_2:
decq %rcx
je .LBB1_3
bsrq %rcx, %rcx
xorq $63, %rcx
jmp .LBB1_5
.LBB1_3:
movl $64, %ecx ; <-- dead
.LBB1_5:
movq $-1, %rax
shrq %cl, %rax
incq %rax
retq
```
And with this PR becomes
```asm
cmpq $2, %rcx
jae .LBB0_2
movl $1, %eax
retq
.LBB0_2:
decq %rcx
bsrq %rcx, %rcx
xorl $63, %ecx
movq $-1, %rax
shrq %cl, %rax
incq %rax
retq
```
Some preparatory refactorings for hash-based DepNodes
This PR collects some changes that turn out to be necessary for implementing `DepNodes` based on stable hashes (see #42294). The commits are self-contained and mostly straightforward.
The most interesting change here is the introduction of `DefIndices` for things that are not part of the AST: Some pieces of crate metadata now have a `DefIndex` too.
cc @eddyb
r? @nikomatsakis
LLVM currently doesn't remove the "bypass if argument is zero" assembly inside branches where the value is known to be non-zero, pessimizing code that uses uN::leading_zeros
Fix setting PATH during linkage on windows-gnu
This makes the behavior almost exactly the same as before the VS2017 patch, except that on MSVC builds the host bin path is no longer added to PATH. I am not sure that's actually necessary on any platform.
r? @alexcrichton
Fixes https://github.com/rust-lang/rust/issues/42422
querify layout and move param env out of the infcx
The main goal of this PR is to move the parameter environment *out* of the inference context. This is because the inference environment will soon be changing over the course of inference --- for example, when we enter into a `for<'a> fn(...)` type, we will push a new environment with an increasing universe index, rather than skolemizing the `'a` references. Similarly, each obligation will soon be able to have a distinct parameter environment, and therefore the `Obligation` struct is extended to carry a `ParamEnv<'tcx>`. (I debated about putting it into the cause; seems plausible, but also weird.)
Along the way, I also reworked how layout works, moving the layout cache into a proper query along the lines of needs-drop and friends.
Finally, tweaks the inference context API. It seemed to be accumulating parameters at an alarming rate. The main way to e.g. make a subtype or equality relationship is to do the following:
infcx.at(cause, param_env).sub(a, b)
infcx.at(cause, param_env).eq(a, b)
In both cases, `a` is considered the "expected" type (this used to be specified by a boolean). I tried hard to preserve the existing notion of what was "expected", although in some cases I'm not convinced it was being set on purpose one way or the other. This is why in some cases you will see me do `sup(b, a)`, which is otherwise equivalent to `sub(a, b)`, but sets the "expected type" differently.
r? @eddyb
cc @arielb1
Support VS 2017
Fixes#38584
This replaces all the MSVC linker logic with that from the 'gcc' crate. The code looks the same, but there could be regressions.
I've only tested this with x86_64.
r? @alexcrichton
cc @vadimcn @retep998
Translate array drop glue using MIR
I was a bit lazy here and used a usize-based index instead of a pointer iteration. Do you think this is important @eddyb?
r? @eddyb
This fixes leakage on panic with arrays & slices. I am using a C-style
for-loop instead of a pointer-based loop because that would be ugly-er
to implement.
Mark various items and fields as private or pub(crate), and remove a function that turns out to be unused.
These are not used anywhere in-tree, but I guess it's a [breaking-change] for plugins.
This support is needed for bindgen to work well on 32-bit Windows, and
also enables people to begin experimenting with C++ FFI support on that
platform.
Fixes#42044.
Use the trait-environment+type as the key. Note that these
are only invoked on types that live for the entire compilation
(no inference artifacts). We no longer need the various special-case
bits and caches that were in place before.
debuginfo: Generate unique DW_AT_names for compilation units to work around OSX linker bug
This should fix issue #39160 and does not seem to cause any problems.
cc @tromey, @Manishearth
r? @jdm
add -Z pre-link-arg{,s} to rustc
This PR adds two unstable flags to `rustc`: `-Z pre-link-arg` and `-Z
pre-link-args`. These are the counterpart of the existing `-C link-arg{,s}`
flags and can be used to pass extra arguments at the *beginning* of the linker
invocation, before the Rust object files are passed.
I have [started] a discussion on the rust-embedded RFCs repo about settling on a
convention for passing extra arguments to the linker and there are two options
on discussion: `.cargo/config`'s `target.$T.rustflags` and custom target
specification files (`{pre,,post}-link-args` fields). However, to compare these
two options on equal footing this `-Z pre-link-arg` feature is required.
[started]: https://github.com/rust-embedded/rfcs/pull/24
Therefore I'm requesting landing this `-Z pre-link-arg` flag as an experimental
feature to evaluate these two options.
cc @brson
r? @alexcrichton
