The mythical MMIX hardware engineers have wisely understood the
need to automatically disable speculation when a speculated
execution path transitions to kernel mode. There might be
mythical talk about using a bit in a configuration register to
enable even that, but that's just speculation and some say
allowing speculation over such mode transitions would be
unresponsible and bad engineering.
gcc:
PR target/86794
* config/mmix/mmix.c (TARGET_HAVE_SPECULATION_SAFE_VALUE): Redefine
to speculation_safe_value_not_needed.
Index: gcc/config/mmix/mmix.c
===================================================================
--- gcc/config/mmix/mmix.c (revision 264163)
+++ gcc/config/mmix/mmix.c (working copy)
@@ -227,6 +224,9 @@
#undef TARGET_CONDITIONAL_REGISTER_USAGE
#define TARGET_CONDITIONAL_REGISTER_USAGE mmix_conditional_register_usage
+#undef TARGET_HAVE_SPECULATION_SAFE_VALUE
+#define TARGET_HAVE_SPECULATION_SAFE_VALUE speculation_safe_value_not_needed
+
#undef TARGET_RTX_COSTS
#define TARGET_RTX_COSTS mmix_rtx_costs
#undef TARGET_ADDRESS_COST
brgds, H-P
