Rollup merge of #121841 - tgross35:f16-f128-step2-intrinsics, r=compiler-errors

`f16` and `f128` step 2: intrinsics

Continuation of rust-lang/rust#121728, another portion of rust-lang/rust#114607.

This PR adds `f16` and `f128` intrinsics, and hooks them up to both HIR and LLVM. This is all still unexposed to the frontend, which will probably be the next step. Also update itanium mangling per `@rcvalle's` in https://github.com/rust-lang/rust/pull/121728/files#r1506570300, and fix a typo from step 1.

Once these types are usable in code, I will add the codegen tests from #114607 (codegen is passing on that branch)

This does add more `unimplemented!`s to Clippy, but I still don't think we can do better until library support is added.

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

Author: Nadrieril

clippy_lints/src/approx_const.rs

@@ -75,9 +75,12 @@ impl ApproxConstant {
     fn check_lit(&self, cx: &LateContext<'_>, lit: &LitKind, e: &Expr<'_>) {
         match *lit {
             LitKind::Float(s, LitFloatType::Suffixed(fty)) => match fty {
+                FloatTy::F16 => self.check_known_consts(cx, e, s, "f16"),
                 FloatTy::F32 => self.check_known_consts(cx, e, s, "f32"),
                 FloatTy::F64 => self.check_known_consts(cx, e, s, "f64"),
+                FloatTy::F128 => self.check_known_consts(cx, e, s, "f128"),
             },
+            // FIXME(f16_f128): add `f16` and `f128` when these types become stable.
             LitKind::Float(s, LitFloatType::Unsuffixed) => self.check_known_consts(cx, e, s, "f{32, 64}"),
             _ => (),
         }

clippy_lints/src/float_literal.rs

@@ -76,8 +76,10 @@ impl<'tcx> LateLintPass<'tcx> for FloatLiteral {
             let digits = count_digits(sym_str);
             let max = max_digits(fty);
             let type_suffix = match lit_float_ty {
+                LitFloatType::Suffixed(ast::FloatTy::F16) => Some("f16"),
                 LitFloatType::Suffixed(ast::FloatTy::F32) => Some("f32"),
                 LitFloatType::Suffixed(ast::FloatTy::F64) => Some("f64"),
+                LitFloatType::Suffixed(ast::FloatTy::F128) => Some("f128"),
                 LitFloatType::Unsuffixed => None,
             };
             let (is_whole, is_inf, mut float_str) = match fty {

clippy_utils/src/consts.rs

@@ -277,12 +277,16 @@ pub fn lit_to_mir_constant<'tcx>(lit: &LitKind, ty: Option<Ty<'tcx>>) -> Constan
         LitKind::Char(c) => Constant::Char(c),
         LitKind::Int(n, _) => Constant::Int(n.get()),
         LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
+            ast::FloatTy::F16 => unimplemented!("f16_f128"),
             ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
             ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
+            ast::FloatTy::F128 => unimplemented!("f16_f128"),
         },
         LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
+            ty::Float(FloatTy::F16) => unimplemented!("f16_f128"),
             ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
             ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
+            ty::Float(FloatTy::F128) => unimplemented!("f16_f128"),
             _ => bug!(),
         },
         LitKind::Bool(b) => Constant::Bool(b),