cranelift: Fix spillslot regression on big-endian platforms

PR 2840 changed the store_spillslot routine to always store
integer registers in full word size to a spill slot.  However,
the load_spillslot routine was not updated, which may causes
the contents to be reloaded in a different type.  On big-endian
systems this will fetch wrong data.

Fixed by using the same type override in load_spillslot.

cranelift/codegen/src/machinst/abi_impl.rs

@@ -1209,6 +1209,15 @@ impl<M: ABIMachineSpec> ABICallee for ABICalleeImpl<M> {
         let spill_off = islot * M::word_bytes() as i64;
         let sp_off = self.stackslots_size as i64 + spill_off;
         trace!("load_spillslot: slot {:?} -> sp_off {}", slot, sp_off);
+
+        // Integer types smaller than word size have been spilled as words below,
+        // and therefore must be reloaded in the same type.
+        let ty = if ty.is_int() && ty.bytes() < M::word_bytes() {
+            M::word_type()
+        } else {
+            ty
+        };
+
         gen_load_stack_multi::<M>(StackAMode::NominalSPOffset(sp_off, ty), into_regs, ty)
     }