Committed, PR target/86794, MMIX TARGET_HAVE_SPECULATION_SAFE_VALUE: Not needed.

Message ID alpine.BSF.2.20.16.1809091431101.31971@arjuna.pair.com
State New
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Series
  • Committed, PR target/86794, MMIX TARGET_HAVE_SPECULATION_SAFE_VALUE: Not needed.
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Commit Message

Hans-Peter Nilsson Sept. 9, 2018, 6:34 p.m.
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.


brgds, H-P

Patch

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