Hi!

This patch is to fix the inconsistent behaviors for non-LTO mode
and LTO mode.  As Martin pointed out, currently the function
rs6000_can_inline_p simply makes it inlinable if callee_tree is
NULL, but it's wrong, we should use the command line options
from target_option_default_node as default.  It also replaces
rs6000_isa_flags with the one from target_option_default_node
when caller_tree is NULL as rs6000_isa_flags could probably
change since initialization.

It also extends the scope of the check for the case that callee
has explicit set options, for test case pr102059-2.c inlining can
happen unexpectedly before, it's fixed accordingly.

As Richi/Mike pointed out, some tuning flags like MASK_P8_FUSION
can be neglected for inlining, this patch also exludes them when
the callee is attributed by always_inline.

Bootstrapped and regtested on powerpc64le-linux-gnu Power9.

BR,
Kewen
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gcc/ChangeLog:

	PR ipa/102059
	* config/rs6000/rs6000.c (rs6000_can_inline_p): Adjust with
	target_option_default_node and consider always_inline_safe flags.

gcc/testsuite/ChangeLog:

	PR ipa/102059
	* gcc.target/powerpc/pr102059-1.c: New test.
	* gcc.target/powerpc/pr102059-2.c: New test.
	* gcc.target/powerpc/pr102059-3.c: New test.
	* gcc.target/powerpc/pr102059-4.c: New test.