builtins: Fix fold_builtin_query clzg/ctzg side-effects handling [PR112639]

builtins: Fix fold_builtin_query clzg/ctzg side-effects handling [PR112639]

As the testcase shows, I've missed one spot where initially the code thinks
it could use 2 argument IFN_CLZ/IFN_CTZ form, but then verifies it can't
because it doesn't have the right target value and turns it into the
arg0 ? arg1 : .C[LT]Z (arg0)
form.  That form evaluates the argument twice though and so needs save_expr,
which I've missed to call in that case.  In other cases where it is known
from the beginning that it will be needed (e.g. the __builtin_clzg case
on types smaller than unsigned int where we'll need to add an addend
to the clz value) or the unsigned __int128 expansion called save_expr
before.

2023-11-21  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/112639
	* builtins.cc (fold_builtin_bit_query): If arg0 has side-effects, arg1
	is specified but cleared, call save_expr on arg0.

	* gcc.dg/torture/pr112639.c: New test.