Iplementing Arrays in LLVM

llvm-arrays.ll

; In JL: int[] a = new int[2];
; In C: int *a = (int*) malloc(2 * sizeof(int));

; In LLVM:

%a = alloca i32*, align 8           
; type of %a = i32 **
; %a is the location on stack which (later) holds the address of the array on the heap

%call = call i8* @malloc(i64 8)    ; notice the size = 8 i.e, (2 * 4) as int is 4 bytes long
%0 = bitcast i8* %call to i32*
store i32* %0, i32** %a, align 8

; In JL: int[][] b = new int[5][2];
; In C:
;    int **b = (int**) malloc(5 * sizeof(int*));
;     for (int i = 0; i < 5; i++) {
;       b[i] = malloc(2 * sizeof(int));
;     }

; In LLVM:

%b = alloca i32**, align 8

%call1 = call i8* @malloc(i64 40)   ; notice the size = 40 i.e, (5 * 8) because an int* is 8 bytes long
%1 = bitcast i8* %call1 to i32**
store i32** %1, i32*** %b, align 8

; LLVM code for the for loop (not included here)