operations is to be performed.
(Note that the vector must be the first operand because of the way that
genrecog.c record positions within an insn.)
- This can occur all by itself in a PATTERN, as a component of a PARALLEL,
- or inside an expression. */
+
+ UNSPEC can occur all by itself in a PATTERN, as a component of a PARALLEL,
+ or inside an expression.
+ UNSPEC by itself or as a component of a PARALLEL
+ is currently considered not deletable.
+
+ FIXME: Replace all uses of UNSPEC that appears by itself or as a component
+ of a PARALLEL with USE.
+ */
DEF_RTL_EXPR(UNSPEC, "unspec", "Ei", RTX_EXTRA)
/* Similar, but a volatile operation and one which may trap. */
/* Indicate something is used in a way that we don't want to explain.
For example, subroutine calls will use the register
- in which the static chain is passed. */
+ in which the static chain is passed.
+
+ USE can not appear as an operand of other rtx except for PARALLEL.
+ USE is not deletable, as it indicates that the operand
+ is used in some unknown way. */
DEF_RTL_EXPR(USE, "use", "e", RTX_EXTRA)
/* Indicate something is clobbered in a way that we don't want to explain.
For example, subroutine calls will clobber some physical registers
- (the ones that are by convention not saved). */
+ (the ones that are by convention not saved).
+
+ CLOBBER can not appear as an operand of other rtx except for PARALLEL.
+ CLOBBER of a hard register appearing by itself (not within PARALLEL)
+ is considered undeletable before reload. */
DEF_RTL_EXPR(CLOBBER, "clobber", "e", RTX_EXTRA)
/* Call a subroutine.