[Bug tree-optimization/53991] _mm_popcnt_u64 fails with -O3 -fgnu-tm

[torvald at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53991

--- Comment #9 from torvald at gcc dot gnu.org ---
Still fails with r232693.

This seems to be another case of difficult ordering between TM passes and other
passes.  It makes sense that we don't inline tm_pure because we must not loose
that information.  always_inline is specified to produce an error when not
inlining, but this shouldn't be much of a problem when considering code
instrumented for transactions I suppose (can there be a case where lack of
inlining causes a correctness problem?).

Perhaps it's easiest if we clone the function if we see such a case, so that
the solution can be different for TM-instrumented clones and normal code.