Auto merge of #121728 - tgross35:f16-f128-step1-ty-updates, r=compiler-errors

Add stubs in IR and ABI for `f16` and `f128`

This is the very first step toward the changes in rust-lang/rust#114607 and the [`f16` and `f128` RFC](https://rust-lang.github.io/rfcs/3453-f16-and-f128.html). It adds the types to `rustc_type_ir::FloatTy` and `rustc_abi::Primitive`, and just propagates those out as `unimplemented!` stubs where necessary.

These types do not parse yet so there is no feature gate, and it should be okay to use `unimplemented!`.

The next steps will probably be AST support with parsing and the feature gate.

r? `@compiler-errors`
cc `@Nilstrieb` suggested breaking the PR up in rust-lang/rust#120645 (comment)

Author: bors

src/type_.rs

@@ -83,8 +83,10 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
 
     pub fn type_float_from_ty(&self, t: ty::FloatTy) -> Type<'gcc> {
         match t {
+            ty::FloatTy::F16 => self.type_f16(),
             ty::FloatTy::F32 => self.type_f32(),
             ty::FloatTy::F64 => self.type_f64(),
+            ty::FloatTy::F128 => self.type_f128(),
         }
     }
 }
@@ -118,13 +120,21 @@ impl<'gcc, 'tcx> BaseTypeMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
         self.isize_type
     }
 
+    fn type_f16(&self) -> Type<'gcc> {
+        unimplemented!("f16_f128")
+    }
+    
     fn type_f32(&self) -> Type<'gcc> {
         self.float_type
     }
 
     fn type_f64(&self) -> Type<'gcc> {
         self.double_type
     }
+    
+    fn type_f128(&self) -> Type<'gcc> {
+        unimplemented!("f16_f128")
+    }
 
     fn type_func(&self, params: &[Type<'gcc>], return_type: Type<'gcc>) -> Type<'gcc> {
         self.context.new_function_pointer_type(None, return_type, params, false)

src/type_of.rs

@@ -6,7 +6,7 @@ use rustc_middle::bug;
 use rustc_middle::ty::{self, Ty, TypeVisitableExt};
 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_target::abi::{self, Abi, Align, F32, F64, FieldsShape, Int, Integer, Pointer, PointeeInfo, Size, TyAbiInterface, Variants};
+use rustc_target::abi::{self, Abi, Align, F16, F128, F32, F64, FieldsShape, Int, Integer, Pointer, PointeeInfo, Size, TyAbiInterface, Variants};
 use rustc_target::abi::call::{CastTarget, FnAbi, Reg};
 
 use crate::abi::{FnAbiGcc, FnAbiGccExt, GccType};
@@ -257,8 +257,10 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
         match scalar.primitive() {
             Int(i, true) => cx.type_from_integer(i),
             Int(i, false) => cx.type_from_unsigned_integer(i),
+            F16 => cx.type_f16(),
             F32 => cx.type_f32(),
             F64 => cx.type_f64(),
+            F128 => cx.type_f128(),
             Pointer(address_space) => {
                 // If we know the alignment, pick something better than i8.
                 let pointee =