Hi!
As the following testcase shows, there are some bugs in the
-fnon-call-exceptions bit-field load lowering. In particular, there
is a case where we want to emit a load early in the initialization
(before m_init_gsi) and because that load might throw exception, need
to split block after the load so that it has an EH edge.
Now, across this splitting, we have m_init_gsi, save_gsi (something
we put back into m_gsi afterwards) statement iterators and m_preheader_bb
which is used to determine the pre-header edge of a loop (if any).
As the testcase shows, both of these statement iterators and m_preheader_bb
as well need adjustments if the block was split. If the stmt iterators
refer to a statement, they need to be updated so that if the statement is
in the bb after the split gsi_bb and gsi_seq is updated, otherwise they
ought to be the start of the new (second) bb.
Similarly, m_preheader_bb should be updated to the second bb if it was
the first before. Other spots where we insert something before m_init_gsi
don't split blocks in there and are fine.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2023-11-23 Jakub Jelinek <ja...@redhat.com>
PR middle-end/112668
* gimple-lower-bitint.cc (bitint_large_huge::handle_load): When
splitting gsi_bb (m_init_gsi) basic block, update m_preheader_bb
if needed, fix up update of m_init_gsi and update saved m_gsi
as well if needed.
* gcc.dg/bitint-40.c: New test.
--- gcc/gimple-lower-bitint.cc.jj 2023-11-14 10:52:16.000000000 +0100
+++ gcc/gimple-lower-bitint.cc 2023-11-22 14:34:17.327140002 +0100
@@ -1687,7 +1687,22 @@ bitint_large_huge::handle_load (gimple *
edge e = split_block (gsi_bb (m_gsi), g);
make_edge (e->src, eh_edge->dest, EDGE_EH)->probability
= profile_probability::very_unlikely ();
- m_init_gsi.bb = e->dest;
+ m_init_gsi = gsi_last_bb (e->dest);
+ if (!gsi_end_p (m_init_gsi))
+ gsi_next (&m_init_gsi);
+ if (gsi_bb (save_gsi) == e->src)
+ {
+ if (gsi_end_p (save_gsi))
+ {
+ save_gsi = gsi_last_bb (e->dest);
+ if (!gsi_end_p (save_gsi))
+ gsi_next (&save_gsi);
+ }
+ else
+ save_gsi = gsi_for_stmt (gsi_stmt (save_gsi));
+ }
+ if (m_preheader_bb == e->src)
+ m_preheader_bb = e->dest;
}
}
m_gsi = save_gsi;
--- gcc/testsuite/gcc.dg/bitint-40.c.jj 2023-11-22 13:47:12.380580107 +0100
+++ gcc/testsuite/gcc.dg/bitint-40.c 2023-11-22 14:35:50.225842768 +0100
@@ -0,0 +1,29 @@
+/* PR middle-end/112668 */
+/* { dg-do compile { target bitint } } */
+/* { dg-options "-std=c23 -fnon-call-exceptions" } */
+
+#if __BITINT_MAXWIDTH__ >= 156
+struct T156 { _BitInt(156) a : 2; unsigned _BitInt(156) b : 135; _BitInt(156)
c : 2; };
+extern void foo156 (struct T156 *);
+
+unsigned _BitInt(156)
+bar156 (int i)
+{
+ struct T156 r156[12];
+ foo156 (&r156[0]);
+ return r156[i].b;
+}
+#endif
+
+#if __BITINT_MAXWIDTH__ >= 495
+struct T495 { _BitInt(495) a : 2; unsigned _BitInt(495) b : 471; _BitInt(495)
c : 2; };
+extern void foo495 (struct T495 *r495);
+
+unsigned _BitInt(495)
+bar495 (int i)
+{
+ struct T495 r495[12];
+ foo495 (r495);
+ return r495[i].b;
+}
+#endif
Jakub
