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Auto merge of #96862 - oli-obk:enum_cast_mir, r=RalfJung

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Change enum->int casts to not go through MIR casts.

follow-up to https://github.com/rust-lang/rust/pull/96814

this simplifies all backends and even gives LLVM more information about the return value of `Rvalue::Discriminant`, enabling optimizations in more cases.
This commit is contained in:
bors 2022-07-05 09:36:29 +00:00
commit 53792b9c5c
21 changed files with 238 additions and 143 deletions
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32
compiler/rustc_const_eval/src/transform/validate.rs
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@ -7,9 +7,9 @@ use rustc_middle::mir::interpret::Scalar;
use rustc_middle::mir::visit::NonUseContext::VarDebugInfo;
use rustc_middle::mir::visit::{PlaceContext, Visitor};
use rustc_middle::mir::{
traversal, AggregateKind, BasicBlock, BinOp, Body, BorrowKind, Local, Location, MirPass,
MirPhase, Operand, Place, PlaceElem, PlaceRef, ProjectionElem, Rvalue, SourceScope, Statement,
StatementKind, Terminator, TerminatorKind, UnOp, START_BLOCK,
traversal, AggregateKind, BasicBlock, BinOp, Body, BorrowKind, CastKind, Local, Location,
MirPass, MirPhase, Operand, Place, PlaceElem, PlaceRef, ProjectionElem, Rvalue, SourceScope,
Statement, StatementKind, Terminator, TerminatorKind, UnOp, START_BLOCK,
};
use rustc_middle::ty::fold::BottomUpFolder;
use rustc_middle::ty::{self, InstanceDef, ParamEnv, Ty, TyCtxt, TypeFoldable};
@ -361,6 +361,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
);
}
}
Rvalue::Ref(..) => {}
Rvalue::Len(p) => {
let pty = p.ty(&self.body.local_decls, self.tcx).ty;
check_kinds!(
@ -503,7 +504,30 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
let a = operand.ty(&self.body.local_decls, self.tcx);
check_kinds!(a, "Cannot shallow init type {:?}", ty::RawPtr(..));
}
_ => {}
Rvalue::Cast(kind, operand, target_type) => {
match kind {
CastKind::Misc => {
let op_ty = operand.ty(self.body, self.tcx);
if op_ty.is_enum() {
self.fail(
location,
format!(
"enum -> int casts should go through `Rvalue::Discriminant`: {operand:?}:{op_ty} as {target_type}",
),
);
}
}
// Nothing to check here
CastKind::PointerFromExposedAddress
| CastKind::PointerExposeAddress
| CastKind::Pointer(_) => {}
}
}
Rvalue::Repeat(_, _)
| Rvalue::ThreadLocalRef(_)
| Rvalue::AddressOf(_, _)
| Rvalue::NullaryOp(_, _)
| Rvalue::Discriminant(_) => {}
}
self.super_rvalue(rvalue, location);
}