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tree-ssa-threadupdate.c (thread_through_all_blocks): Thread blocks is post order.

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* tree-ssa-threadupdate.c (thread_through_all_blocks): Thread
	blocks is post order.

From-SVN: r254752
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Jeff Law 2017-11-14 20:45:03 -07:00 committed by Jeff Law
parent 171a55e7f5
commit 611a7c7e37
2 changed files with 31 additions and 8 deletions
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5
gcc/ChangeLog
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@ -1,3 +1,8 @@
2017-11-14 Jeff Law <law@redhat.com>
* tree-ssa-threadupdate.c (thread_through_all_blocks): Thread
blocks is post order.
2017-11-15 Alexandre Oliva <aoliva@redhat.com>
* dumpfile.h (TDF_COMPARE_DEBUG): New.

34
gcc/tree-ssa-threadupdate.c
View File

@ -2174,7 +2174,6 @@ thread_through_all_blocks (bool may_peel_loop_headers)
{
bool retval = false;
unsigned int i;
bitmap_iterator bi;
struct loop *loop;
auto_bitmap threaded_blocks;
@ -2278,14 +2277,33 @@ thread_through_all_blocks (bool may_peel_loop_headers)
initialize_original_copy_tables ();
/* First perform the threading requests that do not affect
loop structure. */
EXECUTE_IF_SET_IN_BITMAP (threaded_blocks, 0, i, bi)
{
basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i);
/* The order in which we process jump threads can be important.
if (EDGE_COUNT (bb->preds) > 0)
retval |= thread_block (bb, true);
Consider if we have two jump threading paths A and B. If the
target edge of A is the starting edge of B and we thread path A
first, then we create an additional incoming edge into B->dest that
we can not discover as a jump threading path on this iteration.
If we instead thread B first, then the edge into B->dest will have
already been redirected before we process path A and path A will
natually, with no further work, target the redirected path for B.
An post-order is sufficient here. Compute the ordering first, then
process the blocks. */
if (!bitmap_empty_p (threaded_blocks))
{
int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (cfun));
unsigned int postorder_num = post_order_compute (postorder, false, false);
for (unsigned int i = 0; i < postorder_num; i++)
{
unsigned int indx = postorder[i];
if (bitmap_bit_p (threaded_blocks, indx))
{
basic_block bb = BASIC_BLOCK_FOR_FN (cfun, indx);
retval |= thread_block (bb, true);
}
}
free (postorder);
}
/* Then perform the threading through loop headers. We start with the