diff options
Diffstat (limited to '3/8_array_allocation_and_access')
5 files changed, 92 insertions, 0 deletions
diff --git a/3/8_array_allocation_and_access/36_sizes_and_addresses.c b/3/8_array_allocation_and_access/36_sizes_and_addresses.c new file mode 100644 index 0000000..c9b8056 --- /dev/null +++ b/3/8_array_allocation_and_access/36_sizes_and_addresses.c @@ -0,0 +1,11 @@ +// size total size start address element i +short S[7]; +// 2 14 x_s xs + 2 * i +short *T[3]; +// 8 24 x_t x_t + 8 * i +short **U[6]; +// 8 48 x_u x_u + 8 * i +int V[8]; +// 4 32 x_v x_v + 4 * i +double *W[4]; +// 8 32 x_w x_w + 8 * i diff --git a/3/8_array_allocation_and_access/37_array_arithmetic.c b/3/8_array_allocation_and_access/37_array_arithmetic.c new file mode 100644 index 0000000..c2ecbf2 --- /dev/null +++ b/3/8_array_allocation_and_access/37_array_arithmetic.c @@ -0,0 +1,7 @@ +// S and i in rdx and rcx +// type value assembly +// S+1 short * xs + 2 leaq $2(%rdx), %rax, // leaq since we want to store the address not the value +// S[3] short M[xs+6] movw $6(%rdx), %ax +// &S[i] short * xs+2i leaq (rdx, rcx, 2), %rax +// S[4*i+1] short M[xs+8i+2] movw $2(%rdx, %rcx, 8), %ax +// S+i-5 short * xs+2i-10 leaq $-10(%rdx, %rcx, 2), %rax diff --git a/3/8_array_allocation_and_access/38_nested_arrays.c b/3/8_array_allocation_and_access/38_nested_arrays.c new file mode 100644 index 0000000..b53c7be --- /dev/null +++ b/3/8_array_allocation_and_access/38_nested_arrays.c @@ -0,0 +1,18 @@ +#define M 20; +#define N 30; + +long P[5][7]; +long Q[7][5]; + +// i in rdi, j in rsi +// sum_element: +// leaq 0(,%rdi, 8), %rdx %rdx <- 8*i +// subq %rdi, %rdx %rdx <- %rdx - i +// addq %rsi, %rdx %rdx <- %rdx + j +// leaq (%rsi, %rsi, 4), %rax %rax <- 5j +// addq %rax, %rdi %rdi <- %rax + %rdi // rdi <- 5j + i +// movq Q(, %rdi, 8), %rax %rax <- xq + 8(5j + i) +// addq P(, %rdx, 8), %rax %rax <- %rax + xp + 8(7i + j) +long sum_element(long i, long j) { + return P[i][j] + Q[j][i]; +} diff --git a/3/8_array_allocation_and_access/39_explain_rows_cols.c b/3/8_array_allocation_and_access/39_explain_rows_cols.c new file mode 100644 index 0000000..7304f23 --- /dev/null +++ b/3/8_array_allocation_and_access/39_explain_rows_cols.c @@ -0,0 +1,8 @@ +// addq %rdx, %rdi Aptr = xa + 64i +// fix_matrix = int[16][16], so each int is 4 bytes and we need to multiple by the number of columns to find the +// i row, A + L(C*i + j) <=> A + 4(16*i) +// +// leaq (%rsi, %rcx, 4), %rcx Bptr = xb + 4k, this one is simple B + L(C*i + j) <=> B + 4(j), find the first row of the column j +// +// leaq 1024(%rcx), %rsi Bend = xb + 4k + 1024, find the N row of column k, +// B + 4(16*16 + k) <=> B + 1024 + 4k diff --git a/3/8_array_allocation_and_access/40_diagonal_elements.c b/3/8_array_allocation_and_access/40_diagonal_elements.c new file mode 100644 index 0000000..ab541db --- /dev/null +++ b/3/8_array_allocation_and_access/40_diagonal_elements.c @@ -0,0 +1,48 @@ +// A in rdi, val in rsi +// fix_set_diag: +// movl $0, %eax +// .L13 +// movl %esi, (%rdi, %rax) +// addq $68, %rax +// cmpq $1088, %rax +// jne .L13 +// rep; ret +#include <stdio.h> +#define N 16 +typedef int fix_matrix[N][N]; + +void fix_set_diag(fix_matrix A, int val) { + long i; + for (i = 0; i < N; i++) { + A[i][i] = val; + } +} + +void fix_set_diag_opt(fix_matrix A, int val) { + int *Aptr = &A[0][0]; + int *Aend = &A[N][N]; + do { + *Aptr = val; + Aptr += N; // Next row + Aptr ++; // Next column + } while (Aptr != Aend); +} + +int main(void) { + int i, j; + fix_matrix A; + for (i=0; i < N; i++) { + for (j=0; j < N; j++) { + A[i][j] = 0; + } + } + + i, j = 0, 0; + fix_set_diag_opt(A, 1); + for (i=0; i < N; i++) { + for (j=0; j < N; j++) { + printf("%ld", A[i][j]); + } + printf("\n"); + } +} |