test HashMap creation in libstd-MIR, and make it work again

src/terminator/intrinsic.rs

@@ -424,9 +424,10 @@ pub(super) fn call_intrinsic(
                 let ty_align = self.type_align(ty)?;
                 let val_byte = self.value_to_primval(arg_vals[1], u8)?.to_u128()? as u8;
                 let size = self.type_size(ty)?.expect("write_bytes() type must be sized");
-                let ptr = arg_vals[0].read_ptr(&self.memory)?.to_ptr()?;
+                let ptr = arg_vals[0].read_ptr(&self.memory)?;
                 let count = self.value_to_primval(arg_vals[2], usize)?.to_u64()?;
                 if count > 0 {
+                    let ptr = ptr.to_ptr()?;
                     self.memory.check_align(ptr, ty_align, size * count)?;
                     self.memory.write_repeat(ptr, val_byte, size * count)?;
                 }

tests/run-pass-fullmir/hashmap.rs

@@ -1,10 +1,6 @@
 use std::collections::{self, HashMap};
 use std::hash::BuildHasherDefault;
 
-// This disables the test completely:
-// ignore-stage1
-// TODO: The tests actually passes against rustc and miri with MIR-libstd, but right now, we cannot express that in the test flags
-
 fn main() {
     let map : HashMap<String, i32, BuildHasherDefault<collections::hash_map::DefaultHasher>> = Default::default();
     assert_eq!(map.values().fold(0, |x, y| x+y), 0);