Hi!
bb_rank is long and has basic block indexes << 16, and oe rank
is unsigned int.
So, if some function has over 32767 basic blocks, we can run into various
issues.
As I said in the PR, I see 3 possible fixes, one is attached below and
the shortest, which I've bootstrapped/regtested on x86_64-linux and
i686-linux. While it not fix all possible issues, at least if there
aren't way too many basic blocks (2G+) on 64-bit hosts it shouldn't
fail the qsort checking, and on 32-bit hosts also, even when above 64K
basic blocks it is possible two different basic blocks will have the same
rank and we fall through to reassoc_stmt_dominates_stmt_p.
Another possibility is to store bb_rank still as long, but don't << 16
it when initializing, but when using except for this sort_by_operand_rank
spot.
And probably best but most involved change would be to switch to using
uint64_t for bb_rank, phi_rank as well as oe->rank. By reordering fields
in oe it shouldn't make things worse on 64-bit hosts, but for 32-bit hosts
will need more memory; on the other side, it should handle better 32K+ basic
block cases, which even for 32-bit host compilers in some cases can be
handled within the limited 32-bit host address space.
So, is this ok for trunk or should I pick some other option?
2017-11-30 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/83221
* tree-ssa-reassoc.c (sort_by_operand_rank): Shift bb_rank
down by 16.
(init_reassoc): Formatting fix.
--- gcc/tree-ssa-reassoc.c.jj 2017-10-28 09:00:48.000000000 +0200
+++ gcc/tree-ssa-reassoc.c 2017-11-30 16:07:47.220334364 +0100
@@ -543,7 +543,7 @@ sort_by_operand_rank (const void *pa, co
return -1;
/* If neither is, compare bb_rank. */
if (bb_rank[bbb->index] != bb_rank[bba->index])
- return bb_rank[bbb->index] - bb_rank[bba->index];
+ return (bb_rank[bbb->index] >> 16) - (bb_rank[bba->index] >> 16);
}
bool da = reassoc_stmt_dominates_stmt_p (stmta, stmtb);
@@ -6131,7 +6131,7 @@ init_reassoc (void)
/* Set up rank for each BB */
for (i = 0; i < n_basic_blocks_for_fn (cfun) - NUM_FIXED_BLOCKS; i++)
- bb_rank[bbs[i]] = ++rank << 16;
+ bb_rank[bbs[i]] = ++rank << 16;
free (bbs);
calculate_dominance_info (CDI_POST_DOMINATORS);
Jakub
