[Bug target/80160] [7 regression] operand has impossible constraints

[bernds at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80160

--- Comment #4 from Bernd Schmidt <bernds at gcc dot gnu.org> ---
Perhaps this.

Index: lra-assigns.c
===================================================================
--- lra-assigns.c       (revision 246226)
+++ lra-assigns.c       (working copy)
@@ -908,7 +908,8 @@ must_not_spill_p (unsigned spill_regno)
      does not solve the general case where existing reloads fully
      cover a limited register class.  */
   if (!bitmap_bit_p (&non_reload_pseudos, spill_regno)
-      && reg_class_size [reg_preferred_class (spill_regno)] == 1)
+      && reg_class_size [reg_preferred_class (spill_regno)] == 1
+      && reg_alternate_class (spill_regno) == NO_REGS)
     return true;
   return false;
 }