Added building instructions

README.md

-2024-04-10 - Milo - Install cross compiler
+# 2024-04-10 - Milo
+## Install cross compiler
 
 To run the programs we need on ARM we need to setup a cross
 compiler for AArch64. This is actually not too bad.
@@ -13,3 +14,18 @@ Then we move them to an easier path
   `mv gcc-arm-10.3-2021.07-x86_64-aarch64-none-linux-gnu aarch`
 
 Now we can use the cross compiler toolchain to compiler our programs.
+
+## Build programs
+We need to use the cross compiler, and regular compiler to build out programs.
+For both architectures, we need to make sure our binaries are static by using the `-static`
+command line option. This is for gem5 to work.
+
+For AArch64 we need to decide what optimization level we want from gcc.
+Regardless of optimization level we can turn on auto-vectorization with
+-ftree-vectorize
+
+For X86 we need to include an additional flag -msse (or -msse2 not sure).
+
+We can get more info from the compiler by passing in the -ftree-vectorize-verbose=LEVEL flag.
+
+For more info go to [here](https://gcc.gnu.org/projects/tree-ssa/vectorization.html)