recog: Fix propagation into ASM_OPERANDS

recog: Fix propagation into ASM_OPERANDS

An inline asm with multiple output operands is represented as a
parallel set in which the SET_SRCs are the same (shared) ASM_OPERANDS.
insn_propagation didn't account for this, and instead propagated
into each ASM_OPERANDS individually.  This meant that it could
apply a substitution X->Y to Y itself, which (a) could create
circularity and (b) would be semantically wrong in any case,
since Y might use a different value of X.

This patch checks explicitly for parallels involving ASM_OPERANDS,
just like combine does.

gcc/
	* recog.cc (insn_propagation::apply_to_pattern_1): Handle shared
	ASM_OPERANDS.