PR middle-end/79499

	* function.c (thread_prologue_and_epilogue_insns): Determine blocks
	for find_many_sub_basic_blocks bitmap by looking up BLOCK_FOR_INSN
	of first NONDEBUG_INSN_P in each of the split_prologue_seq and
	prologue_seq sequences - if any.

	* gcc.dg/pr79499.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-7-branch@250815 138bc75d-0d04-0410-961f-82ee72b054a4

4 files changed, 55 insertions, 7 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9f50c861262..83797525fb4 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2017-08-02  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/79499
+	* function.c (thread_prologue_and_epilogue_insns): Determine blocks
+	for find_many_sub_basic_blocks bitmap by looking up BLOCK_FOR_INSN
+	of first NONDEBUG_INSN_P in each of the split_prologue_seq and
+	prologue_seq sequences - if any.
+
 2017-08-01  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/81641
diff --git a/gcc/function.c b/gcc/function.c
index 9cfe58afe90..b3de845af8a 100644
--- a/gcc/function.c
+++ b/gcc/function.c
@@ -6057,20 +6057,42 @@ thread_prologue_and_epilogue_insns (void)
 
   if (split_prologue_seq || prologue_seq)
     {
+      rtx_insn *split_prologue_insn = split_prologue_seq;
       if (split_prologue_seq)
-	insert_insn_on_edge (split_prologue_seq, orig_entry_edge);
+	{
+	  while (split_prologue_insn && !NONDEBUG_INSN_P (split_prologue_insn))
+	    split_prologue_insn = NEXT_INSN (split_prologue_insn);
+	  insert_insn_on_edge (split_prologue_seq, orig_entry_edge);
+	}
 
+      rtx_insn *prologue_insn = prologue_seq;
       if (prologue_seq)
-	insert_insn_on_edge (prologue_seq, entry_edge);
+	{
+	  while (prologue_insn && !NONDEBUG_INSN_P (prologue_insn))
+	    prologue_insn = NEXT_INSN (prologue_insn);
+	  insert_insn_on_edge (prologue_seq, entry_edge);
+	}
 
       commit_edge_insertions ();
 
       /* Look for basic blocks within the prologue insns.  */
-      auto_sbitmap blocks (last_basic_block_for_fn (cfun));
-      bitmap_clear (blocks);
-      bitmap_set_bit (blocks, entry_edge->dest->index);
-      bitmap_set_bit (blocks, orig_entry_edge->dest->index);
-      find_many_sub_basic_blocks (blocks);
+      if (split_prologue_insn
+	  && BLOCK_FOR_INSN (split_prologue_insn) == NULL)
+	split_prologue_insn = NULL;
+      if (prologue_insn
+	  && BLOCK_FOR_INSN (prologue_insn) == NULL)
+	prologue_insn = NULL;
+      if (split_prologue_insn || prologue_insn)
+	{
+	  auto_sbitmap blocks (last_basic_block_for_fn (cfun));
+	  bitmap_clear (blocks);
+	  if (split_prologue_insn)
+	    bitmap_set_bit (blocks,
+			    BLOCK_FOR_INSN (split_prologue_insn)->index);
+	  if (prologue_insn)
+	    bitmap_set_bit (blocks, BLOCK_FOR_INSN (prologue_insn)->index);
+	  find_many_sub_basic_blocks (blocks);
+	}
     }
 
   default_rtl_profile ();
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 8171bfc28a4..47a4fe024e7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-08-02  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/79499
+	* gcc.dg/pr79499.c: New test.
+
 2017-08-01  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/81641
diff --git a/gcc/testsuite/gcc.dg/pr79499.c b/gcc/testsuite/gcc.dg/pr79499.c
new file mode 100644
index 00000000000..509549ff2fd
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr79499.c
@@ -0,0 +1,13 @@
+/* PR middle-end/79499 */
+/* { dg-do compile { target split_stack } } */
+/* { dg-options "-O2 -fsplit-stack -fno-omit-frame-pointer" } */
+
+struct S { struct S *a, *b; };
+
+void
+foo (struct S *x)
+{
+  do
+    x->b = x->a;
+  while (x = x->a);
+}