Windows x86: Change i128 to return via the vector ABI

Clang and GCC both return `i128` in xmm0 on windows-msvc and
windows-gnu. Currently, Rust returns the type on the stack. Add a
calling convention adjustment so we also return scalar `i128`s using the
vector ABI, which makes our `i128` compatible with C.

In the future, Clang may change to return `i128` on the stack for its
`-msvc` targets (more at [1]). If this happens, the change here will
need to be adjusted to only affect MinGW.

Link: https://github.com/rust-lang/rust/issues/134288

compiler/rustc_codegen_cranelift/src/cast.rs

@@ -96,25 +96,9 @@ pub(crate) fn clif_int_or_float_cast(
                 },
             );
 
-            if fx.tcx.sess.target.is_like_windows {
-                let ret = fx.lib_call(
-                    &name,
-                    vec![AbiParam::new(from_ty)],
-                    vec![AbiParam::new(types::I64X2)],
-                    &[from],
-                )[0];
-                // FIXME(bytecodealliance/wasmtime#6104) use bitcast instead of store to get from i64x2 to i128
-                let ret_ptr = fx.create_stack_slot(16, 16);
-                ret_ptr.store(fx, ret, MemFlags::trusted());
-                ret_ptr.load(fx, types::I128, MemFlags::trusted())
-            } else {
-                fx.lib_call(
-                    &name,
-                    vec![AbiParam::new(from_ty)],
-                    vec![AbiParam::new(types::I128)],
-                    &[from],
-                )[0]
-            }
+            fx.lib_call(&name, vec![AbiParam::new(from_ty)], vec![AbiParam::new(types::I128)], &[
+                from,
+            ])[0]
         } else if to_ty == types::I8 || to_ty == types::I16 {
             // FIXME implement fcvt_to_*int_sat.i8/i16
             let val = if to_signed {