Auto merge of #121926 - tgross35:f16-f128-step3-feature-gate, r=compiler-errors,petrochenkov

`f16` and `f128` step 3: compiler support & feature gate

Continuation of https://github.com/rust-lang/rust/pull/121841, another portion of https://github.com/rust-lang/rust/pull/114607

This PR exposes the new types to the world and adds a feature gate. Marking this as a draft because I need some feedback on where I did the feature gate check. It also does not yet catch type via suffixed literals (so the feature gate test will fail, probably some others too because I haven't belssed).

If there is a better place to check all types after resolution, I can do that. If not, I figure maybe I can add a second gate location in AST when it checks numeric suffixes.

Unfortunately I still don't think there is much testing to be done for correctness (codegen tests or parsed value checks) until we have basic library support. I think that will be the next step.

Tracking issue: https://github.com/rust-lang/rust/issues/116909

r? `@compiler-errors`
cc `@Nilstrieb`
`@rustbot` label +F-f16_and_f128

2 files changed, 64 insertions, 2 deletions

diff --git a/compiler/rustc_middle/src/mir/interpret/value.rs b/compiler/rustc_middle/src/mir/interpret/value.rs
index e937c17c8ac..24d4a79c7d7 100644
--- a/compiler/rustc_middle/src/mir/interpret/value.rs
+++ b/compiler/rustc_middle/src/mir/interpret/value.rs
@@ -3,7 +3,7 @@ use std::fmt;
 use either::{Either, Left, Right};
 
 use rustc_apfloat::{
-    ieee::{Double, Single},
+    ieee::{Double, Half, Quad, Single},
     Float,
 };
 use rustc_macros::HashStable;
@@ -202,6 +202,11 @@ impl<Prov> Scalar<Prov> {
     }
 
     #[inline]
+    pub fn from_f16(f: Half) -> Self {
+        Scalar::Int(f.into())
+    }
+
+    #[inline]
     pub fn from_f32(f: Single) -> Self {
         Scalar::Int(f.into())
     }
@@ -211,6 +216,11 @@ impl<Prov> Scalar<Prov> {
         Scalar::Int(f.into())
     }
 
+    #[inline]
+    pub fn from_f128(f: Quad) -> Self {
+        Scalar::Int(f.into())
+    }
+
     /// This is almost certainly not the method you want!  You should dispatch on the type
     /// and use `to_{u8,u16,...}`/`scalar_to_ptr` to perform ptr-to-int / int-to-ptr casts as needed.
     ///
@@ -423,6 +433,11 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
     }
 
     #[inline]
+    pub fn to_f16(self) -> InterpResult<'tcx, Half> {
+        self.to_float()
+    }
+
+    #[inline]
     pub fn to_f32(self) -> InterpResult<'tcx, Single> {
         self.to_float()
     }
@@ -431,4 +446,9 @@ impl<'tcx, Prov: Provenance> Scalar<Prov> {
     pub fn to_f64(self) -> InterpResult<'tcx, Double> {
         self.to_float()
     }
+
+    #[inline]
+    pub fn to_f128(self) -> InterpResult<'tcx, Quad> {
+        self.to_float()
+    }
 }
diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index a70e01645f4..71d7dfd8b01 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -1,4 +1,4 @@
-use rustc_apfloat::ieee::{Double, Single};
+use rustc_apfloat::ieee::{Double, Half, Quad, Single};
 use rustc_apfloat::Float;
 use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
@@ -370,6 +370,11 @@ impl ScalarInt {
     }
 
     #[inline]
+    pub fn try_to_f16(self) -> Result<Half, Size> {
+        self.try_to_float()
+    }
+
+    #[inline]
     pub fn try_to_f32(self) -> Result<Single, Size> {
         self.try_to_float()
     }
@@ -378,6 +383,11 @@ impl ScalarInt {
     pub fn try_to_f64(self) -> Result<Double, Size> {
         self.try_to_float()
     }
+
+    #[inline]
+    pub fn try_to_f128(self) -> Result<Quad, Size> {
+        self.try_to_float()
+    }
 }
 
 macro_rules! from {
@@ -450,6 +460,22 @@ impl TryFrom<ScalarInt> for char {
     }
 }
 
+impl From<Half> for ScalarInt {
+    #[inline]
+    fn from(f: Half) -> Self {
+        // We trust apfloat to give us properly truncated data.
+        Self { data: f.to_bits(), size: NonZero::new((Half::BITS / 8) as u8).unwrap() }
+    }
+}
+
+impl TryFrom<ScalarInt> for Half {
+    type Error = Size;
+    #[inline]
+    fn try_from(int: ScalarInt) -> Result<Self, Size> {
+        int.to_bits(Size::from_bytes(2)).map(Self::from_bits)
+    }
+}
+
 impl From<Single> for ScalarInt {
     #[inline]
     fn from(f: Single) -> Self {
@@ -482,6 +508,22 @@ impl TryFrom<ScalarInt> for Double {
     }
 }
 
+impl From<Quad> for ScalarInt {
+    #[inline]
+    fn from(f: Quad) -> Self {
+        // We trust apfloat to give us properly truncated data.
+        Self { data: f.to_bits(), size: NonZero::new((Quad::BITS / 8) as u8).unwrap() }
+    }
+}
+
+impl TryFrom<ScalarInt> for Quad {
+    type Error = Size;
+    #[inline]
+    fn try_from(int: ScalarInt) -> Result<Self, Size> {
+        int.to_bits(Size::from_bytes(16)).map(Self::from_bits)
+    }
+}
+
 impl fmt::Debug for ScalarInt {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // Dispatch to LowerHex below.