Code Generation

First, we need to understand how and where variables are stored in memory, because that is a large part of how we generate code for them.

Where are Variables Stored?

Local variables are stored in the function’s stack frame

The typical addressing mode is [SP, #pimm]

Global variables are stored at locations named by labels

The typical addressing mode is label
Need to use ADRP and ADR instructions to reach the address

Code Generation for Basic Types

C Source Code	Type	A64 Assembly Code
`int x, y, z *w`	`NA`	`x is in memory at [sp, #24], y @ [sp, #20], z @ [sp, #16], w @ [sp #8]`
`x = 2`	`int`	`mov w9, #2` `str w9, [sp, #24]`
`y=x`	`int`	`ldr w9, [sp, #24` `str w9, [sp, #20]`
`x++`	`int`	`ldr w9, [sp, #24]` `add w9, w9, #1` `str w9, [sp, #24]`
`y -= x`	`int`	`ldr w10, [sp, #24]` `ldr w9, [sp, #20]` `subs w9, w9, w10` `str w9, [sp, #20]`
`z = x + y - 4`	`int`	`ldr w10, [sp, #24]` `ldr w9, [sp, #20]` `add w9, w9, w10` `subs w9, w9, #4` `str w9, [sp, #16]`
`w = &x`	`int*`	`add x8, sp, #24` `str x8, [sp, #8]`
`z = *w`	`int`	`ldr x10, [sp, #8] // load W` `ldr w9, [x10] // load X` `str w9, [sp, #16] // store in Z`
`unsigned i, int *E`		`i @ [sp #60]` `E @ [sp, #48]`
`int x = E[i]`		`ldr x8, [sp, #48]` `ldr w9, [sp, #60]` `ldr w8, [x8, x9,`