Enable early inlining into always_inline functions

Enable early inlining into always_inline functions

Early inliner currently skips always_inline functions and moreover we ignore
calls from always_inline in ipa_reverse_postorder.  This leads to disabling
most of propagation done using early optimization that is quite bad when
early inline functions are not leaf functions, which is now quite common
in libstdc++.

This patch instead of fully disabling the inline checks calls in callee.
I am quite conservative about what can be inlined as this patch is bit
touchy anyway.  To avoid problems with always_inline being optimized
after early inline I extended inline_always_inline_functions to lazilly
compute fnsummary when needed.

gcc/ChangeLog:

	PR middle-end/110334
	* ipa-fnsummary.h (ipa_fn_summary): Add
	safe_to_inline_to_always_inline.
	* ipa-inline.cc (can_early_inline_edge_p): ICE
	if SSA is not built; do cycle checking for
	always_inline functions.
	(inline_always_inline_functions): Be recrusive;
	watch for cycles; do not updat overall summary.
	(early_inliner): Do not give up on always_inlines.
	* ipa-utils.cc (ipa_reverse_postorder): Do not skip
	always inlines.

gcc/testsuite/ChangeLog:

	PR middle-end/110334
	* g++.dg/opt/pr66119.C: Disable early inlining.
	* gcc.c-torture/compile/pr110334.c: New test.
	* gcc.dg/tree-ssa/pr110334.c: New test.