#define DEBUG 0 #if DEBUG #include #endif int B[4]; int A[4][4][4][4]; static int __attribute__((noinline)) foo (void) { int i, j, k, l; /* Loops (L, J) are interchanged, and then loops (J and K) are interchanged. The result is a nest starting with (K, J, L). */ for (l = 0; l < 4; l++) { for (k = 0; k < 4; k++) { for (j = 0; j < 4; j++) { for (i = 0; i < 2; i++) { B[i] = A[i][k][j][l] + A[3 - i][k][j][l]; B[3 - i] = A[i][k][j][l] - A[3 - i][k][j][l]; } A[0][k][j][l] = B[0] + B[1]; A[2][k][j][l] = B[0] - B[1]; A[1][k][j][l] = B[3] + B[2]; A[3][k][j][l] = B[3] - B[2]; } for (i = 0; i < 4; i++) { for (j = 0; j < 2; j++) { B[j] = A[i][k][j][l] + A[i][k][3 - j][l]; B[3 - j] = A[i][k][j][l] - A[i][k][3 - j][l]; } A[i][k][0][l] = B[0] + B[1]; A[i][k][2][l] = B[0] - B[1]; A[i][k][1][l] = B[3] + B[2]; A[i][k][3][l] = B[3] - B[2]; } } } return A[0][1][0][2] + A[0][3][0][3] + A[0][2][0][2] + A[0][1][0][1] + A[3][3][0][2]; } extern void abort (); int main (void) { int i, j, k, l, res; for (i = 0; i < 4; i++) B[i] = 2; for (i = 0; i < 4; i++) for (j = 0; j < 4; j++) for (k = 0; k < 4; k++) for (l = 0; l < 4; l++) A[i][j][k][l] = i + j + k + l; res = foo (); #if DEBUG for (i = 0; i < 4; i++) for (j = 0; j < 4; j++) for (k = 0; k < 4; k++) for (l = 0; l < 4; l++) fprintf (stderr, "A[%d][%d][%d][%d] = %d \n", i, j, k, l, A[i][j][k][l]); fprintf (stderr, "res = %d \n", res); #endif if (res != 424) abort (); return 0; } /* { dg-final { scan-tree-dump-times "will be interchanged" 2 "graphite" } } */ /* { dg-final { cleanup-tree-dump "graphite" } } */