diff mbox

[2/5] dce: Don't dead-code delete separately wrapped restores

Message ID e8a1ae7870bbbd8d70d55483b24e014d0c4713fe.1474616087.git.segher@kernel.crashing.org
State New
Headers show

Commit Message

Segher Boessenkool Sept. 23, 2016, 8:21 a.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 after this).
This happens with gcc.dg/torture/pr53168.c, for example.


2016-09-23  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(+)

Comments

Jeff Law Sept. 26, 2016, 4:39 p.m. UTC | #1 
On 09/23/2016 02:21 AM, Segher Boessenkool wrote:
> 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 after this).
> This happens with gcc.dg/torture/pr53168.c, for example.
>
>
> 2016-09-23  Segher Boessenkool  <segher@kernel.crashing.org>
>
> 	* dce.c (delete_unmarked_insns): Don't delete instructions with
> 	a REG_CFA_RESTORE note.
OK and can go in now IMHO.
jeff
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));