Hi Jan, hi Sebastian,
while looking in the graphite backend code I stepped over a commit
(r138161) introducing graphite_loops_mapping.
At the moment I do not understand perfectly for what it is used, as it
seems to mirror a feature I already implemented (see graphite.h):
---------------------------------------------------------------
/* LOOPS contains for every column in the graphite domain the
corresponding
gimple loop. If there exists no corresponding gimple loop LOOPS
contains
NULL.
Example:
Original code:
for (i = 0; i <= 20; i++)
for (j = 5; j <= 10; j++)
A
Original domain:
(I)eq i j 1
1 1 0 0 # i >= 0
1 -1 0 20 # i <= 20
1 0 1 0 # j >= 0
1 0 -1 10 # j <= 10
Original loops vector:
0 1
Loop i Loop j
After some changes (Exchange i and j, strip-mine i):
Domain:
(I)eq j ii i k 1
1 0 0 1 0 0 # i >= 0
1 0 0 -1 0 20 # i <= 20
1 1 0 0 0 0 # j >= 0
1 -1 0 0 0 10 # j <= 10
1 0 -1 1 0 0 # ii <= i
1 0 1 -1 0 1 # ii + 1 >= i
1 0 -1 0 2 0 # ii <= 2k
1 0 1 0 -2 0 # ii >= 2k
Iterator vector:
0 1 2 3
Loop j NULL Loop i NULL
Means the original loop i is now at column two of the domain and
loop j in the original loop nest is now at column 0. Column 1 and
3 are emtpy. */
VEC (loop_p, heap) *loops;
/* Returns the gimple loop, that corresponds to the loop_iterator_INDEX.
If there is no corresponding gimple loop, we return NULL. */
static inline loop_p
gbb_loop_at_index (graphite_bb_p gb, int index);
/* Returns the corresponding loop iterator index for a gimple loop. */
static inline int
gbb_loop_index (graphite_bb_p gb, loop_p loop);
---------------------------------------------------------------
During your commit you removed my code from the graphite_trans_*
functions.
Can you explain why you decided to replace GBB_LOOPS with loops_mapping?
Where there any shortcomings in my implementation or did you need some
different features?
Is GBB_LOOPS completely replaced by loops_mapping? In this case I will
remove the remaining parts of GBB_LOOPS.
It would be great, if you could add some documentation for
loops_mapping, as I am not sure, if I understand your code correct.
It seems, that you make a mapping from SCOP_LOOPS() to the index in the
cloog matrices. I think, that this is not always possible.
If we have for example a loop A in SCOP_LOOPS (), that we split during
graphite into two loops B1, B2. The first loop, B1, can be blocked the
second one, B2, not.
So we get for the A->B1 a different mapping as for A->B2.
Thanks
Tobi
