Truncated bits while writing value to registers of RISC-V
Description of problem:
As mentioned above
Steps to reproduce:
```
# 1. Compile the `test.S`:
riscv32-unknown-linux-gnu-gcc -g -static -nostartfiles -o test hello.S

# 2. Execute the binary:
qemu-riscv32 ./test

# 3. Check exit code
echo $?
```