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Add CastKind::Transmute to MIR

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Updates `interpret`, `codegen_ssa`, and `codegen_cranelift` to consume the new cast instead of the intrinsic.

Includes `CastTransmute` for custom MIR building, to be able to test the extra UB.
This commit is contained in:
Scott McMurray 2023-02-24 18:32:52 -08:00
parent a266f11990
commit 64cce5fc7d
55 changed files with 955 additions and 190 deletions
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26
compiler/rustc_mir_transform/src/lower_intrinsics.rs
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@ -221,6 +221,32 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
terminator.kind = TerminatorKind::Goto { target };
}
}
sym::transmute => {
let dst_ty = destination.ty(local_decls, tcx).ty;
let Ok([arg]) = <[_; 1]>::try_from(std::mem::take(args)) else {
span_bug!(
terminator.source_info.span,
"Wrong number of arguments for transmute intrinsic",
);
};
// Always emit the cast, even if we transmute to an uninhabited type,
// because that lets CTFE and codegen generate better error messages
// when such a transmute actually ends up reachable.
block.statements.push(Statement {
source_info: terminator.source_info,
kind: StatementKind::Assign(Box::new((
*destination,
Rvalue::Cast(CastKind::Transmute, arg, dst_ty),
))),
});
if let Some(target) = *target {
terminator.kind = TerminatorKind::Goto { target };
} else {
terminator.kind = TerminatorKind::Unreachable;
}
}
_ if intrinsic_name.as_str().starts_with("simd_shuffle") => {
validate_simd_shuffle(tcx, args, terminator.source_info.span);
}