https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51840
--- Comment #6 from Kai Tietz <ktietz at gcc dot gnu.org> ---
So this is a source of endless bugs ... and all are related to merging of
basic-blocks.
By the following patch the sample can be built successful on x64 targets.
There seems to be another issue for x86 targets triggered in some cases. For
32-bit the factoring out of partial addresses to register leads to new
basic-blocks placed before blocks actually jumped by table. Major issue happens
in mergephi pass.
For all of those problems is common that we happily operate on forced
user-labels.
Index: tree-cfgcleanup.c
===================================================================
--- tree-cfgcleanup.c (Revision 212070)
+++ tree-cfgcleanup.c (Arbeitskopie)
@@ -285,12 +285,19 @@ tree_forwarder_block_p (basic_block bb, bool phi_w
for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
{
gimple stmt = gsi_stmt (gsi);
+ tree lbl;
switch (gimple_code (stmt))
{
case GIMPLE_LABEL:
- if (DECL_NONLOCAL (gimple_label_label (stmt)))
+ lbl = gimple_label_label (stmt);
+ if (DECL_NONLOCAL (lbl))
return false;
+ /* If PHI_WANTED is true, we can't operate on user-labels.
+ See PR 51840. */
+ if (phi_wanted
+ && !DECL_ARTIFICIAL (lbl) && FORCED_LABEL (lbl))
+ return false;
if (optimize == 0 && gimple_location (stmt) != locus)
return false;
break;
