Copy byval argument to local stackslot if alignment is insufficient#1641
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0xmuon wants to merge 3 commits intorust-lang:mainfrom
Open
Copy byval argument to local stackslot if alignment is insufficient#16410xmuon wants to merge 3 commits intorust-lang:mainfrom
0xmuon wants to merge 3 commits intorust-lang:mainfrom
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bjorn3
requested changes
Apr 13, 2026
bjorn3
requested changes
Apr 15, 2026
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| let len = ty::Const::from_target_usize(fx.tcx, arg_abi.layout.size.bytes()); | ||
| let bytes_ty = fx.tcx.mk_ty_from_kind(ty::Array(fx.tcx.types.u8, len)); |
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This can use Ty::new_array().
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| pub(super) struct ArgValue<'tcx> { | ||
| pub(super) value: Option<CValue<'tcx>>, | ||
| pub(super) underaligned_pointee_align: Option<Align>, |
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This can now be a bool is_underaligned_pointee.
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| Normal(ArgValue<'tcx>), | ||
| Spread(Vec<ArgValue<'tcx>>), |
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Maybe pull out the Option around the field ty and have:
Suggested change
| Normal(ArgValue<'tcx>), | |
| Spread(Vec<ArgValue<'tcx>>), | |
| Normal(Option<ArgValue<'tcx>>), | |
| Spread(Vec<Option<ArgValue<'tcx>>>), |
? The align field is unused when the argument is not passed at all. I don't know how much that would complicate cvalue_for_param though.
| let arg_abi = arg_abis_iter.next().unwrap(); | ||
| fx.caller_location = | ||
| Some(cvalue_for_param(fx, None, None, arg_abi, &mut block_params_iter).unwrap()); | ||
| let arg = cvalue_for_param(fx, None, None, arg_abi, &mut block_params_iter); |
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Maybe assert that arg is not underaligned?
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fix: #1465
Copy the underaligned
byval(indirect) arguments into a local stackslot when the incoming pointer alignment is less than the Rust ABI alignment. This avoids miscompiles from assuming stronger alignment than the ABI guarantees.