diff mbox

[2/6] dce: Don't dead-code delete separately wrapped restores

Message ID 3a4933c2886d6618cfe151797d8b5e8023c850b7.1475501415.git.segher@kernel.crashing.org
State New
Headers show

Commit Message

Segher Boessenkool Oct. 3, 2016, 1:48 p.m. UTC 
If there is a separately wrapped register restore on some path that
is dead (say, control goes into an endless loop after it), then we
cannot delete that restore because that would confuse the DWARF CFI
(if there is another path joining).
This happens with gcc.dg/torture/pr53168.c, for example.


2016-06-07  Segher Boessenkool  <segher@kernel.crashing.org>

	* dce.c (delete_unmarked_insns): Don't delete instructions with
	a REG_CFA_RESTORE note.

---
 gcc/dce.c | 9 +++++++++
 1 file changed, 9 insertions(+)
diff mbox

Patch

diff --git a/gcc/dce.c b/gcc/dce.c
index ea3fb00..d510287 100644
--- a/gcc/dce.c
+++ b/gcc/dce.c
@@ -587,6 +587,15 @@  delete_unmarked_insns (void)
 	  if (!dbg_cnt (dce))
 	    continue;
 
+	  if (crtl->shrink_wrapped_separate
+	      && find_reg_note (insn, REG_CFA_RESTORE, NULL))
+	    {
+	      if (dump_file)
+		fprintf (dump_file, "DCE: NOT deleting insn %d, it's a "
+				    "callee-save restore\n", INSN_UID (insn));
+	      continue;
+	    }
+
 	  if (dump_file)
 	    fprintf (dump_file, "DCE: Deleting insn %d\n", INSN_UID (insn));