pub fn mr(&mut self, addr: u32) -> (MemoryReadRecord, u32) {
        let record =
            self.rt.mr(addr, self.current_shard, self.clk, Some(&mut self.local_memory_access));
        (record, record.value)
    }
Read a word from memory.

`addr` must be a pointer to main memory, not a register.
crates/core/executor/src/syscalls/context.rs