lower-bitint: Fix up -fnon-call-exceptions bit-field load lowering [PR112668]

Message ID ZV8eh+8HZl/ejibp@tucnak
State Unresolved
Headers
Series lower-bitint: Fix up -fnon-call-exceptions bit-field load lowering [PR112668] |

Checks

Context Check Description
snail/gcc-patch-check warning Git am fail log

Commit Message

Jakub Jelinek Nov. 23, 2023, 9:42 a.m. UTC
  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  <jakub@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.


	Jakub
  

Patch

--- 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