[PATCH] dwarf2cfi: Dump row differences before asserting

Segher Boessenkool segher@kernel.crashing.org
Mon Oct 31 17:16:00 GMT 2016

If maybe_record_trace_start fails because the CFI is inconsistent on two
paths into a block it currently just ICEs.  This changes it to also dump
the CFI on those two paths in the dump file; debugging it without that
information is hopeless.

Tested on powerpc64-linux {-m32,-m64}.  Is this okay for trunk?


2016-10-31  Segher Boessenkool  <segher@kernel.crashing.org>

	* dwarf2cfi.c (dump_cfi_row): Add forward declaration.
	(maybe_record_trace_start): If the CFI is different on the new and
	old paths, print out both to the dump file before ICEing.

 gcc/dwarf2cfi.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/gcc/dwarf2cfi.c b/gcc/dwarf2cfi.c
index da9da52..19edc28 100644
--- a/gcc/dwarf2cfi.c
+++ b/gcc/dwarf2cfi.c
@@ -2239,6 +2239,8 @@ add_cfis_to_fde (void)
+static void dump_cfi_row (FILE *f, dw_cfi_row *row);
 /* If LABEL is the start of a trace, then initialize the state of that
    trace from CUR_TRACE and CUR_ROW.  */
@@ -2282,7 +2284,21 @@ maybe_record_trace_start (rtx_insn *start, rtx_insn *origin)
       /* We ought to have the same state incoming to a given trace no
 	 matter how we arrive at the trace.  Anything else means we've
 	 got some kind of optimization error.  */
-      gcc_checking_assert (cfi_row_equal_p (cur_row, ti->beg_row));
+      if (!cfi_row_equal_p (cur_row, ti->beg_row))
+	{
+	  if (dump_file)
+	    {
+	      fprintf (dump_file, "Inconsistent CFI state!\n");
+	      fprintf (dump_file, "SHOULD have:\n");
+	      dump_cfi_row (dump_file, ti->beg_row);
+	      fprintf (dump_file, "DO have:\n");
+	      dump_cfi_row (dump_file, cur_row);
+	    }
+	  gcc_unreachable ();
+	}
       /* The args_size is allowed to conflict if it isn't actually used.  */
       if (ti->beg_true_args_size != args_size)

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