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This allows generators to overlap fields using variants.
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We relax the assumption that the discriminant is always field 0, in
preparations for layouts like generators where this is not going to be
the case.
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By using 'impl trait', it's possible to create a self-referential
type as follows:
fn foo() -> impl Copy { foo }
This is a function which returns itself.
Normally, the signature of this function would be impossible
to write - it would look like 'fn foo() -> fn() -> fn() ...'
e.g. a function which returns a function, which returns a function...
Using 'impl trait' allows us to avoid writing this infinitely long
type. While it's useless for practical purposes, it does compile and run
However, issues arise when we try to generate llvm debuginfo for such a
type. All 'impl trait' types (e.g. ty::Opaque) are resolved when we
generate debuginfo, which can lead to us recursing back to the original
'fn' type when we try to process its return type.
To resolve this, I've modified debuginfo generation to account for these
kinds of weird types. Unfortunately, there's no 'correct' debuginfo that
we can generate - 'impl trait' does not exist in debuginfo, and this
kind of recursive type is impossible to directly represent.
To ensure that we emit *something*, this commit emits dummy
debuginfo/type names whenever it encounters a self-reference. In
practice, this should never happen - it's just to ensure that we can
emit some kind of debuginfo, even if it's not particularly meaningful
Fixes #58463
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rustc_target: factor out common fields of non-Single Variants.
@tmandry and I were discussing ways to generalize the current variants/discriminant layout to allow more fields in the "`enum`" (or another multi-variant types, such as potentially generator state, in the future), shared by all variants, than just the tag/niche discriminant.
This refactor should make it easier to extend multi-variant layouts, as nothing is duplicating anymore between "tagged enums" and "niche-filling enums".
r? @oli-obk
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Fix invalid DWARF for enums when using ThinLTO
We were setting the same identifier for both the DW_TAG_structure_type
and the DW_TAG_variant_part. This becomes a problem when using ThinLTO
becauses it uses the identifier as a key for a map of types that is used
to delete duplicates based on the ODR, so one of them is deleted as a
duplicate, resulting in invalid DWARF.
The DW_TAG_variant_part isn't a standalone type, so it doesn't need
an identifier. Fix by omitting its identifier.
ODR uniquing is [enabled here](https://github.com/rust-lang/rust/blob/f21dee2c6179276321a88a63300dce74ff707e92/src/rustllvm/PassWrapper.cpp#L1101).
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Add FromStr impl for NonZero types
This is a WIP implementation because I do have some questions regarding the solution.
Somebody should ping the lang team on this I guess.
Please see the annotations on the code for more details.
Closes #58604
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Fix according to oli-obk
(https://github.com/rust-lang/rust/pull/58717#issuecomment-477494457)
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and bump llvm version in test
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We were setting the same identifier for both the DW_TAG_structure_type
and the DW_TAG_variant_part. This becomes a problem when using thinlto
becauses it uses the identifier as a key for a map of types that is used
to delete duplicates based on the ODR, so one of them is deleted as a
duplicate, resulting in invalid DWARF.
The DW_TAG_variant_part isn't a standalone type, so it doesn't need
an identifier. Fix by omitting its identifier.
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Since commit 9452a8dfa3ba, the new debug info format is only generated
for LLVM 8 and newer versions. However, the tests still assume that LLVM
7 will use the new debug info format. Fix the tests (and a comment in
the code) to match the actual version check.
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Address the review comments by simplifying the version check to
just "< 8".
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Issue 57762 points out a compiler crash when the compiler was built
using a stock LLVM 7. LLVM 7 was released without a necessary fix for
a bug in the DWARF discriminant code.
This patch changes rustc to use the fallback mode on (non-Rust) LLVM 7.
Closes #57762
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should be a pure refactoring.
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Add template parameter debuginfo to generic types
This changes debuginfo generation to add template parameters to
generic types. With this change the DWARF now has
DW_TAG_template_type_param for types, not just for functions, like:
<2><40d>: Abbrev Number: 6 (DW_TAG_structure_type)
<40e> DW_AT_name : (indirect string, offset: 0x375): Generic<i32>
<412> DW_AT_byte_size : 4
<413> DW_AT_alignment : 4
...
<3><41f>: Abbrev Number: 8 (DW_TAG_template_type_param)
<420> DW_AT_type : <0x42a>
<424> DW_AT_name : (indirect string, offset: 0xa65e): T
Closes #9224
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This changes debuginfo generation to add template parameters to
generic types. With this change the DWARF now has
DW_TAG_template_type_param for types, not just for functions, like:
<2><40d>: Abbrev Number: 6 (DW_TAG_structure_type)
<40e> DW_AT_name : (indirect string, offset: 0x375): Generic<i32>
<412> DW_AT_byte_size : 4
<413> DW_AT_alignment : 4
...
<3><41f>: Abbrev Number: 8 (DW_TAG_template_type_param)
<420> DW_AT_type : <0x42a>
<424> DW_AT_name : (indirect string, offset: 0xa65e): T
Closes #9224
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Fix emission of niche-filling discriminant values
Bug #55606 points out a regression introduced by #54004; namely that
an assertion can erroneously fire when a niche-filling discriminant
value is emitted.
This fixes the bug by removing the assertion, and furthermore by
arranging for the discriminant value to be masked according to the
size of the niche. This makes handling the discriminant a bit simpler
for debuggers.
The test case is from Jonathan Turner.
Closes #55606
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Bug #55606 points out a regression introduced by #54004; namely that
an assertion can erroneously fire when a niche-filling discriminant
value is emitted.
This fixes the bug by removing the assertion, and furthermore by
arranging for the discriminant value to be masked according to the
size of the niche. This makes handling the discriminant a bit simpler
for debuggers.
The test case is from Jonathan Turner.
Closes #55606
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Implement the rotate_left and rotate_right operations using
llvm.fshl and llvm.fshr if they are available (LLVM >= 7).
Originally I wanted to expose the funnel_shift_left and
funnel_shift_right intrinsics and implement rotate_left and
rotate_right on top of them. However, emulation of funnel
shifts requires emitting a conditional to check for zero shift
amount, which is not necessary for rotates. I was uncomfortable
doing that here, as I don't want to rely on LLVM to optimize
away that conditional (and for variable rotates, I'm not sure it
can). We should revisit that question when we raise our minimum
version requirement to LLVM 7 and don't need emulation code
anymore.
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@eddyb pointed out in review that the niche value computation had a
possible integer overflow problem, fixed here as he suggested.
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This fixes the issues pointed out in review.
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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 #32920
Closes #32924
Closes #52762
Closes #53153
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Cleanup the rest of codegen_llvm
- improve common patterns
- convert string literals with `to_owned`
- remove explicit `return`s
- whitespace & formatting improvements
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