or1k: Fix ICE in libgcc caused by recent validate_subreg changes

After commit eb2ea476db2 ("emit-rtl: Allow extra checks for
paradoxical subregs [PR119966]") paradoxical subregs or the OpenRISC
condition flag register (reg:BI sr_f) are no longer allowed.

This causes and ICE in the ce1 pass which tries to get the or1k flag
register into an SI register, which is no longer possible.

Adjust or1k_can_change_mode_class to allow changing the or1k flag reg to
SI mode which in turn allows paradoxical subregs to be generated again.

gcc/ChangeLog:

	PR target/120587
	* config/or1k/or1k.cc (or1k_can_change_mode_class): Allow
	changing flags mode from BI to SI to allow for paradoxical
	subregs.

diff --git a/gcc/config/or1k/or1k.cc b/gcc/config/or1k/or1k.cc
index 62e2168e0ee38f68571ce19e40eaf68077de26be..f1c92c6bf6c9d24b6d20dfd760cfd6da5d987ccb 100644 (file)
--- a/gcc/config/or1k/or1k.cc
+++ b/gcc/config/or1k/or1k.cc
@@ -1408,8 +1408,9 @@ static bool
 or1k_can_change_mode_class (machine_mode from, machine_mode to,
                            reg_class_t rclass)
 {
+  /* Allow cnoverting special flags to SI mode subregs.  */
   if (rclass == FLAG_REGS)
-    return from == to;
+    return from == to || (from == BImode && to == SImode);
   return true;
 }