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Auto merge of #109521 - tmiasko:const-prop-validation, r=wesleywiser

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Don't validate constants in const propagation

Validation is neither necessary nor desirable.

The constant validation is already omitted at mir-opt-level >= 3, so there there are not changes in MIR test output (the propagation of invalid constants is covered by an existing test in tests/mir-opt/const_prop/invalid_constant.rs).
This commit is contained in:
bors 2023-05-02 03:42:37 +00:00
commit 5133e15459
23 changed files with 247 additions and 40 deletions
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28
compiler/rustc_mir_transform/src/const_prop.rs
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@ -21,9 +21,9 @@ use rustc_target::spec::abi::Abi as CallAbi;
use crate::MirPass;
use rustc_const_eval::interpret::{
self, compile_time_machine, AllocId, ConstAllocation, ConstValue, CtfeValidationMode, Frame,
ImmTy, Immediate, InterpCx, InterpResult, LocalValue, MemoryKind, OpTy, PlaceTy, Pointer,
Scalar, StackPopCleanup,
self, compile_time_machine, AllocId, ConstAllocation, ConstValue, Frame, ImmTy, Immediate,
InterpCx, InterpResult, LocalValue, MemoryKind, OpTy, PlaceTy, Pointer, Scalar,
StackPopCleanup,
};
/// The maximum number of bytes that we'll allocate space for a local or the return value.
@ -464,16 +464,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
return None;
}
// Do not try creating references, nor any types with potentially-complex
// invariants. This avoids an issue where checking validity would do a
// bunch of work generating a nice message about the invariant violation,
// only to not show it to anyone (since this isn't the lint).
Rvalue::Cast(CastKind::Transmute, op, dst_ty) if !dst_ty.is_primitive() => {
trace!("skipping Transmute of {:?} to {:?}", op, dst_ty);
return None;
}
// There's no other checking to do at this time.
Rvalue::Aggregate(..)
| Rvalue::Use(..)
@ -591,18 +581,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
}
trace!("attempting to replace {:?} with {:?}", rval, value);
if let Err(e) = self.ecx.const_validate_operand(
value,
vec![],
// FIXME: is ref tracking too expensive?
// FIXME: what is the point of ref tracking if we do not even check the tracked refs?
&mut interpret::RefTracking::empty(),
CtfeValidationMode::Regular,
) {
trace!("validation error, attempt failed: {:?}", e);
return;
}
// FIXME> figure out what to do when read_immediate_raw fails
let imm = self.ecx.read_immediate_raw(value).ok();