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- # zad5
- ---
- `eliminacji wspólnych podwyrażeń` - wykrywanie i eliminacja powtarzajacych się obliczeń
- ```c
- long neigh(long a[], long n, long i, long j) {
- long ul = a[(i-1)*n + (j-1)];
- long ur = a[(i-1)*n + (j+1)];
- long dl = a[(i+1)*n - (j-1)];
- long dr = a[(i+1)*n - (j+1)];
- return ul + ur + dl + dr;
- }
- ```
- ```nasm
- argumenty:
- a[] - rdi
- n - rsi
- i - rdx
- j - rcx
- neigh:
- decq %rdx ; rdx = i - 1
- leaq -1(%rcx), %r8 ; r8 = j - 1
- incq %rcx ; rcx = j + 1
- imulq %rsi, %rdx ; rdx = (i - 1) * n
- addq %rsi, %rsi ; rsi = 2n
- addq %rdx, %rsi ; rsi = 2n + (i - 1) * n = (i + 1) * n
- leaq (%rdx,%r8), %r9 ; r9 = (i - 1) * n + j - 1
- addq %rcx, %rdx ; rdx = (i - 1) * n + j + 1
- movq (%rdi,%rdx,8), %rax ; rax = a[(i - 1) * n + (j + 1)]
- movq %rsi, %rdx ; rdx = (i + 1) * n
- subq %rcx, %rsi ; rsi = (i + 1) * n - j - 1
- addq (%rdi,%r9,8), %rax ; rax += a[(i - 1) * n + (j - 1)]
- subq %r8, %rdx ; rdx = (i + 1) * n - j + 1
- addq (%rdi,%rdx,8), %rax ; rax += a[(i + 1) * n - (j - 1)]
- addq (%rdi,%rsi,8), %rax ; rax += a[(i + 1) * n - (j + 1)]
- ret
- 2; r8 = j - 1
- 3; rcx = j + 1
- 4; rdx = (i - 1) * n
- 5; rsi = (i + 1) * n
- decq %rdx ; rdx = i - 1
- leaq -1(%rcx), %r8 ; r8 = j - 1
- incq %rcx ; rcx = j + 1
- imulq %rsi, %rdx ; rdx = (i - 1) * n
- leaq (%rdx,%rsi,2), %rsi ; rsi = (i + 1) * n
- movq %rsi, %r9 ; r9 = (i + 1) * n
- addq %r8, %r9 ; r9 = (i + 1) * n + (j - 1)
- movq (%rdi, %r9, 8), %rax ; rax = [ul]
- addq $2, %r9 ; r9 = (i + 1) * n + (j + 1)
- addq (%rdi, %r9, 8), %rax ; rax = [ul] + [ur]
- subq %rcx, %rdx ; rdx = (i - 1) * n - (j + 1)
- addq (%rdi, %rdx, 8), rax ; rax = [ul] + [ur] + [dr]
- addq $2, %rdx ; rdx = (i - 1) * n - (j - 1)
- addq (%rdi, %rdx, 8), rax ; gg
- ret
- ```
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