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Support creating float constants in rustc_public mir #159472

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Merged
rust-bors merged 1 commit into from
Jul 21, 2026
+25 −2
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Support creating float constants in rustc_public mir #159472

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20 changes: 18 additions & 2 deletions compiler/rustc_public/src/compiler_interface.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ use crate::mir::{BinOp, Body, Place, UnOp};
use crate::target::{MachineInfo, MachineSize};
use crate::ty::{
AdtDef, AdtKind, Allocation, AssocItem, Asyncness, ClosureDef, ClosureKind, Constness,
CoroutineDef, Discr, FieldDef, FnDef, ForeignDef, ForeignItemKind, ForeignModule,
CoroutineDef, Discr, FieldDef, FloatTy, FnDef, ForeignDef, ForeignItemKind, ForeignModule,
ForeignModuleDef, GenericArgs, GenericPredicates, Generics, ImplDef, ImplTrait, IntrinsicDef,
LineInfo, MirConst, PolyFnSig, RigidTy, Span, TraitDecl, TraitDef, TraitRef, Ty, TyConst,
TyConstId, TyKind, UintTy, VariantDef, VariantIdx, VtblEntry,
Expand Down Expand Up @@ -514,7 +514,7 @@ impl<'tcx> CompilerInterface<'tcx> {
self.with_cx(|tables, cx| cx.new_const_bool(value).stable(tables, cx))
}

/// Create a new constant that represents the given value.
/// Create a new integer constant that represents the given value.
pub(crate) fn try_new_const_uint(
&self,
value: u128,
Expand All @@ -526,6 +526,22 @@ impl<'tcx> CompilerInterface<'tcx> {
})
}

/// Create a new float constant that represents the given value.
/// The value is the binary representation of the float constant.
/// Example: `try_new_const_float(2.5_f32.to_bits() as u128, FloatTy::F32)`.
pub(crate) fn try_new_const_float(
&self,
value: u128,
float_ty: FloatTy,
) -> Result<MirConst, Error> {
let mut tables = self.tables.borrow_mut();
let cx = &*self.cx.borrow();
let ty = cx.new_rigid_ty(RigidTy::Float(float_ty).internal(&mut *tables, cx.tcx));
// We use `try_new_const_uint` here since it is capable of constructing all scalars in the mir
// that are not pointer.
cx.try_new_const_uint(value, ty).map(|cnst| cnst.stable(&mut *tables, cx))

@celinval celinval Jul 19, 2026

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I think it might be worth creating a bridge for creating a float constant. This function eventually creates a Scalar::Integer. In practice it may not matter, but it's fragile.

@hkalbasi hkalbasi Jul 20, 2026

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I had such a function in my original patch, then I found out that it is identical to try_new_const_uint. I added some comment to explain uint usage is not a mistake here, but I can add a distinct function in the bridge or rename the existing one if it is desired.

@celinval celinval Jul 20, 2026

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Sorry, I read this wrong. I think this is fine as is. Thanks

}

pub(crate) fn try_new_ty_const_uint(
&self,
value: u128,
Expand Down
7 changes: 7 additions & 0 deletions compiler/rustc_public/src/ty.rs
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Expand Up @@ -212,6 +212,13 @@ impl MirConst {
pub fn try_from_uint(value: u128, uint_ty: UintTy) -> Result<MirConst, Error> {
with(|cx| cx.try_new_const_uint(value, uint_ty))
}

/// Build a new constant that represents the given floating point number.
/// The value is the binary representation of the float constant.
/// Example: `try_from_float(2.5_f32.to_bits() as u128, FloatTy::F32)`.
pub fn try_from_float(value: u128, float_ty: FloatTy) -> Result<MirConst, Error> {
with(|cx| cx.try_new_const_float(value, float_ty))
}
}

#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
Expand Down
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