x86-32 float return for 'Rust' ABI: treat all float types consistently

Author: RalfJung

compiler/rustc_ty_utils/src/abi.rs

@@ -1,11 +1,11 @@
 use std::iter;
 
-use rustc_abi::Float::*;
 use rustc_abi::Primitive::{Float, Pointer};
 use rustc_abi::{Abi, AddressSpace, PointerKind, Scalar, Size};
 use rustc_hir as hir;
 use rustc_hir::lang_items::LangItem;
 use rustc_middle::bug;
+use rustc_middle::mir::interpret::PointerArithmetic;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::layout::{
     FnAbiError, HasParamEnv, HasTyCtxt, LayoutCx, LayoutOf, TyAndLayout, fn_can_unwind,
@@ -702,30 +702,19 @@ fn fn_abi_adjust_for_abi<'tcx>(
                 // change their ABIs.
                 && abi != SpecAbi::RustIntrinsic
             {
-                match arg.layout.abi {
-                    // Handle similar to the way arguments with an `Abi::Aggregate` abi are handled
-                    // below, by returning arguments up to the size of a pointer (32 bits on x86)
-                    // cast to an appropriately sized integer.
-                    Abi::Scalar(s) if s.primitive() == Float(F32) => {
-                        // Same size as a pointer, return in a register.
-                        arg.cast_to(Reg::i32());
-                        return;
-                    }
-                    Abi::Scalar(s) if s.primitive() == Float(F64) => {
-                        // Larger than a pointer, return indirectly.
-                        arg.make_indirect();
-                        return;
-                    }
-                    Abi::ScalarPair(s1, s2)
-                        if matches!(s1.primitive(), Float(F32 | F64))
-                            || matches!(s2.primitive(), Float(F32 | F64)) =>
-                    {
+                let has_float = matches!(arg.layout.abi, Abi::Scalar(s) if matches!(s.primitive(), Float(_)))
+                    || matches!(arg.layout.abi, Abi::ScalarPair(s1, s2)
+                        if matches!(s1.primitive(), Float(_)) || matches!(s2.primitive(), Float(_)));
+                if has_float {
+                    if arg.layout.size <= tcx.pointer_size() {
+                        // Same size or smaller than pointer, return in a register.
+                        arg.cast_to(Reg { kind: RegKind::Integer, size: arg.layout.size });
+                    } else {
                         // Larger than a pointer, return indirectly.
                         arg.make_indirect();
-                        return;
                     }
-                    _ => {}
-                };
+                    return;
+                }
             }
 
             match arg.layout.abi {