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michaelwoerister:dont-merge-vtables-when-debuginfo, r=WaffleLapkin
Don't merge vtables when full debuginfo is enabled.
This PR makes the compiler not emit the `unnamed_addr` attribute for vtables when full debuginfo is enabled, so that they don't get merged even if they have the same contents. This allows debuggers to more reliably map from a dyn pointer to the self-type of a trait object by looking at the vtable's debuginfo.
The PR only changes the behavior of the LLVM backend as other backends don't emit vtable debuginfo (as far as I can tell).
The performance impact of this change should be small as [measured](https://github.com/rust-lang/rust/pull/103514#issuecomment-1290833854) in a previous PR.
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Implement `SpecOptionPartialEq` for `cmp::Ordering`
Noticed as I continue to explore options for having code using `partial_cmp` optimize better.
Before:
```llvm
; Function Attrs: mustprogress nofree nosync nounwind willreturn uwtable
define noundef zeroext i1 `@ordering_eq(i8` noundef %0, i8 noundef %1) unnamed_addr #0 {
start:
%2 = icmp eq i8 %0, 2
br i1 %2, label %bb1.i, label %bb3.i
bb1.i: ; preds = %start
%3 = icmp eq i8 %1, 2
br label %"_ZN55_$LT$T$u20$as$u20$core..option..SpecOptionPartialEq$GT$2eq17hb7e7beacecde585fE.exit"
bb3.i: ; preds = %start
%.not.i = icmp ne i8 %1, 2
%4 = icmp eq i8 %0, %1
%spec.select.i = and i1 %.not.i, %4
br label %"_ZN55_$LT$T$u20$as$u20$core..option..SpecOptionPartialEq$GT$2eq17hb7e7beacecde585fE.exit"
"_ZN55_$LT$T$u20$as$u20$core..option..SpecOptionPartialEq$GT$2eq17hb7e7beacecde585fE.exit": ; preds = %bb1.i, %bb3.i
%.0.i = phi i1 [ %3, %bb1.i ], [ %spec.select.i, %bb3.i ]
ret i1 %.0.i
}
```
After:
```llvm
; Function Attrs: mustprogress nofree norecurse nosync nounwind readnone willreturn uwtable
define noundef zeroext i1 `@ordering_eq(i8` noundef %0, i8 noundef %1) unnamed_addr #1 {
start:
%2 = icmp eq i8 %0, %1
ret i1 %2
}
```
(Which <https://alive2.llvm.org/ce/z/-rop5r> says LLVM *could* just do itself, but there's probably an issue already open for that problem from when this was originally looked at for `Option<NonZeroU8>` and friends.)
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...and remove it from `PointeeInfo`, which isn't meant for this.
There are still various places (marked with FIXMEs) that assume all pointers
have the same size and alignment. Fixing this requires parsing non-default
address spaces in the data layout string, which will be done in a followup.
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Implement `alloc::vec::IsZero` for `Option<$NUM>` types
Fixes #106911
Mirrors the `NonZero$NUM` implementations with an additional `assert_zero_valid`.
`None::<i32>` doesn't stricly satisfy `IsZero` but for the purpose of allocating we can produce more efficient codegen.
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bump failing assembly & codegen tests from LLVM 14 to LLVM 15
These tests need LLVM 15.
Found by ```@Robert-Cunningham``` in https://github.com/rust-lang/rust/pull/100601#issuecomment-1385400008
Passed tests at 006506e93fc80318ebfd7939fe1fd4dc19ecd8cb in https://github.com/rust-lang/rust/actions/runs/3942442730/jobs/6746104740.
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Previously, it was only put on scalars with range validity invariants
like bool, was uninit was obviously invalid for those.
Since then, we have normatively declared all uninit primitives to be
undefined behavior and can therefore put `noundef` on them.
The remaining concern was the `mem::uninitialized` function, which cause
quite a lot of UB in the older parts of the ecosystem. This function now
doesn't return uninit values anymore, making users of it safe from this
change.
The only real sources of UB where people could encounter uninit
primitives are `MaybeUninit::uninit().assume_init()`, which has always
be clear in the docs about being UB and from heap allocations (like
reading from the spare capacity of a vec. This is hopefully rare enough
to not break anything.
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Tracking issue: https://github.com/rust-lang/rust/issues/65815
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