Hi!
The following testcase ICEs on s390x-linux, because we have 2 registers
saved in prologue, but only one of them modified in one path and then
both restored there; cprop_hardreg propagates the saving register into the
REG_CFA_RESTORE insn, making it a noop move (we don't really need to restore
it), and then RTL DCE removes the noop move and we ICE during dwarf2 pass,
because of a CFI mismatch.
The following patch makes sure that such insns are not actually removed, but
turned into a USE still holding the note, which is all we need for CFI.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2018-03-15 Jakub Jelinek <ja...@redhat.com>
PR debug/84875
* dce.c (delete_unmarked_insns): Don't remove frame related noop moves
holding REG_CFA_RESTORE notes, instead turn them into a USE.
* gcc.dg/pr84875.c: New test.
--- gcc/dce.c.jj 2018-01-26 12:47:34.255931988 +0100
+++ gcc/dce.c 2018-03-15 14:23:11.553002165 +0100
@@ -569,9 +569,19 @@ delete_unmarked_insns (void)
FOR_BB_INSNS_REVERSE_SAFE (bb, insn, next)
if (NONDEBUG_INSN_P (insn))
{
+ rtx turn_into_use = NULL_RTX;
+
/* Always delete no-op moves. */
if (noop_move_p (insn))
- ;
+ {
+ if (RTX_FRAME_RELATED_P (insn))
+ turn_into_use
+ = find_reg_note (insn, REG_CFA_RESTORE, NULL);
+ if (turn_into_use && REG_P (XEXP (turn_into_use, 0)))
+ turn_into_use = XEXP (turn_into_use, 0);
+ else
+ turn_into_use = NULL_RTX;
+ }
/* Otherwise rely only on the DCE algorithm. */
else if (marked_insn_p (insn))
@@ -611,8 +621,19 @@ delete_unmarked_insns (void)
if (CALL_P (insn))
must_clean = true;
- /* Now delete the insn. */
- delete_insn_and_edges (insn);
+ if (turn_into_use)
+ {
+ /* Don't remove frame related noop moves if they cary
+ REG_CFA_RESTORE note, while we don't need to emit any code,
+ we need it to emit the CFI restore note. */
+ PATTERN (insn)
+ = gen_rtx_USE (GET_MODE (turn_into_use), turn_into_use);
+ INSN_CODE (insn) = -1;
+ df_insn_rescan (insn);
+ }
+ else
+ /* Now delete the insn. */
+ delete_insn_and_edges (insn);
}
/* Deleted a pure or const call. */
--- gcc/testsuite/gcc.dg/pr84875.c.jj 2018-03-15 14:28:02.811159065 +0100
+++ gcc/testsuite/gcc.dg/pr84875.c 2018-03-15 14:27:35.473144347 +0100
@@ -0,0 +1,28 @@
+/* PR debug/84875 */
+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+/* { dg-additional-options "-fpie" { target pie } } */
+/* { dg-additional-options "-march=z196" { target s390*-*-* } } */
+
+static long *a[100];
+static int b[100];
+long *c;
+int d;
+void foo (long *);
+
+void
+bar ()
+{
+ long *g = c;
+ g--;
+ d = *g;
+ if (d)
+ if (b[d] < 8)
+ {
+ *(void **)g = a[d];
+ a[d] = g;
+ b[d]++;
+ return;
+ }
+ foo (g);
+}
Jakub
