Fix ICE on const eval of union field
MIR's `Const::get_field()` attempts to retrieve the value for a given field in a constant. In the case of a union constant it was falling through to a generic `const_get_elt` based on the field index. As union fields don't have an index this caused an ICE in `llvm_field_index`.
Fix by simply returning the current value when accessing any field in a union. This works because all union fields start at byte offset 0.
The added test uses `const_fn` it ensure the field is extracted using MIR's const evaluation. The crash is reproducible without it, however.
Fixes#47788
r? @eddyb
Use the slice length to hint the optimizer about iter.position result
Using the len of the iterator doesn't give the same result.
That's also why we can't generalize it to all TrustedLen iterators.
Problem demo: https://godbolt.org/g/MXg2ae
Fix demo: https://godbolt.org/g/P8q5aZ
Second attempt of #47333
Third attempt of #45501Fixes#45964
Correctly format `extern crate` conflict resolution help
Closes#45799. Follow up to @Cldfire's #45820.
If the `extern` statement that will have a suggestion ends on a `;`, synthesize a new span that doesn't include it.
rustc: Load the `rustc_trans` crate at runtime
Building on the work of #45684 this commit updates the compiler to
unconditionally load the `rustc_trans` crate at runtime instead of linking to it
at compile time. The end goal of this work is to implement #46819 where rustc
will have multiple backends available to it to load.
This commit starts off by removing the `extern crate rustc_trans` from the
driver. This involved moving some miscellaneous functionality into the
`TransCrate` trait and also required an implementation of how to locate and load
the trans backend. This ended up being a little tricky because the sysroot isn't
always the right location (for example `--sysroot` arguments) so some extra code
was added as well to probe a directory relative to the current dll (the
rustc_driver dll).
Rustbuild has been updated accordingly as well to have a separate compilation
invocation for the `rustc_trans` crate and assembly it accordingly into the
sysroot. Finally, the distribution logic for the `rustc` package was also
updated to slurp up the trans backends folder.
A number of assorted fallout changes were included here as well to ensure tests
pass and such, and they should all be commented inline.
Building on the work of # 45684 this commit updates the compiler to
unconditionally load the `rustc_trans` crate at runtime instead of linking to it
at compile time. The end goal of this work is to implement # 46819 where rustc
will have multiple backends available to it to load.
This commit starts off by removing the `extern crate rustc_trans` from the
driver. This involved moving some miscellaneous functionality into the
`TransCrate` trait and also required an implementation of how to locate and load
the trans backend. This ended up being a little tricky because the sysroot isn't
always the right location (for example `--sysroot` arguments) so some extra code
was added as well to probe a directory relative to the current dll (the
rustc_driver dll).
Rustbuild has been updated accordingly as well to have a separate compilation
invocation for the `rustc_trans` crate and assembly it accordingly into the
sysroot. Finally, the distribution logic for the `rustc` package was also
updated to slurp up the trans backends folder.
A number of assorted fallout changes were included here as well to ensure tests
pass and such, and they should all be commented inline.
Fix never-type rvalue ICE
This fixes#43061.
r? @nikomatsakis
A small post-mortem as a follow-up to our investigations in https://github.com/rust-lang/rust/pull/47291:
The problem as I understand it is that when `NeverToAny` coercions are made, the expression/statement that is coerced may be enclosed in a block. In our case, the statement `x;` was being transformed to something like: `NeverToAny( {x;} )`. Then, `NeverToAny` is transformed into an expression:
000fbbc9b8/src/librustc_mir/build/expr/into.rs (L52-L59)
Which ends up calling `ast_block_stmts` on the block `{x;}`, which triggers this condition:
000fbbc9b8/src/librustc_mir/build/block.rs (L141-L147)
In our case, there is no return expression, so `push_assign_unit` is called. But the block has already been recorded as _diverging_, meaning the result of the block will be assigned to a location of type `!`, rather than `()`. This causes the MIR error.
I'm assuming the `NeverToAny` coercion code is doing what it's supposed to (there don't seem to be any other problems), so fixing the issue simply consists of checking that the destination for the return value actually _is_ supposed to be a unit. (If no return value is given, the only other possible type for the return value is `!`, which can just be ignored, as it will be unreachable anyway.)
I checked the other cases of `push_assign_unit`, and it didn't look like they could be affected by the divergence issue (blocks are kind of special-cased in this regard as far as I can tell), so this should be sufficient to fix the issue.
Libtest json output
A revisit to my [last PR](https://github.com/rust-lang/rust/pull/45923).
Events are now more atomic, printed in a flat hierarchy.
For the normal test output:
```
running 1 test
test f ... FAILED
failures:
---- f stdout ----
thread 'f' panicked at 'assertion failed: `(left == right)`
left: `3`,
right: `4`', f.rs:3:1
note: Run with `RUST_BACKTRACE=1` for a backtrace.
failures:
f
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out
```
The JSON equivalent is:
```
{ "type": "suite", "event": "started", "test_count": "1" }
{ "type": "test", "event": "started", "name": "f" }
{ "type": "test", "event": "failed", "name": "f" }
{ "type": "suite", "event": "failed", "passed": 0, "failed": 1, "allowed_fail": 0, "ignored": 0, "measured": 0, "filtered_out": "0" }
{ "type": "test_output", "name": "f", "output": "thread 'f' panicked at 'assertion failed: `(left == right)`
left: `3`,
right: `4`', f.rs:3:1
note: Run with `RUST_BACKTRACE=1` for a backtrace.
" }
```
For E0277 on `for` loops, point at the "head" expression
When E0277's span points at a `for` loop, the actual issue is in the
element being iterated. Instead of pointing at the entire loop, point
only at the first line (when possible) so that the span ends in the
element for which E0277 was triggered.
MIR's `Const::get_field()` attempts to retrieve the value for a given
field in a constant. In the case of a union constant it was falling
through to a generic `const_get_elt` based on the field index. As union
fields don't have an index this caused an ICE in `llvm_field_index`.
Fix by simply returning the current value when accessing any field in a
union. This works because all union fields start at byte offset 0.
The added test uses `const_fn` it ensure the field is extracted using
MIR's const evaluation. The crash is reproducible without it, however.
Fixes#47788
Match libunwind's EABI selection with libpanic_unwind
Currently, the `libunwind` crate will only select the ARM EABI if it is compiling for ARM/Linux or Android targets. `libpanic_unwind`, however, will choose the ARM EABI if the target arch is ARM and the OS is not iOS. This means that if one tries to enable unwinding for a non-standard ARM target (such as implementing a custom stdlib via Xargo, for example), then the two crates can potentially disagree about which EABI is being targeted.
This PR makes `libunwind` use the [same logic](https://github.com/rust-lang/rust/blob/master/src/libpanic_unwind/gcc.rs#L139-L146) as `libpanic_unwind` when choosing the EABI.
I noticed there are a few comments about certain functions only differing on Android or ARM/Linux, but I *think* that those differences apply to the ARM EABI in general. Let me know if I'm wrong about that.
