docs: update requirements

Author: tinkerrc

README.md

@@ -3,6 +3,8 @@
 A tool for testing compiler optimization by compiling the same code under
 various optimization levels and comparing emulation results.
 
+Currently, only x86 is supported.
+
 Name subject to change.
 
 ## Requirements
@@ -11,18 +13,23 @@ Name subject to change.
 poetry install
 ```
 
+Please ensure that the target LLVM binaries are in PATH.
+
+In addition, download and `make` CSmith runtime files in home directory (i.e.
+`~/csmith/runtime`).  In the future, the location of the runtime directory will
+be changed into a command-line option that defaults to the system install
+location of libcsmith0 package.
+
+For [IRFuzzer](https://github.com/SecurityLab-UCD/IRFuzzer)-related program
+providers such as `irfuzzer` and `mutate-csmith`, please ensure that the
+MutatorDriver is compiled and present in PATH.
+
 ## Example
 
 ```shell
-# assemble into ELF format
-as foo.a.s -o foo.a.elf
-as foo.b.s -o foo.b.elf
-# copy executable code out of ELF format
-objcopy -O binary foo.a.elf foo.a.bin
-objcopy -O binary foo.b.elf foo.b.bin
-# emulate and compare
-./sem.py --arch x86 --mode 64 --count 10000 --seed 12345 foo.{a,b}.bin
+# -e 0: Use all cores to compare -O0 and -O3
+./sem.py -p mutate-csmith -e 0 -o ./experiment -O03
 ```
 
-If you encounter an "Invalid instruction" error, chances are Unicorn Engine /
-QEMU does not support the associated CPU extension yet.
+To terminate, Ctrl+C and run `pkill -f sem.py`. Relevant program seeds can be
+found in the specified output directory.