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H A Darch_helpers.hfd092be23982c160a3855f1e396b7311b5225bf9 Thu Mar 26 04:18:48 UTC 2020 Masahiro Yamada <yamada.masahiro@socionext.com> Add get_current_el_maybe_constant()

There are some cases where we want to run EL-dependent code in the
shared code.

We could use #ifdef, but it leaves slight possibility where we do not
know the exception level at the build-time (e.g. library code).

The counter approach is to use get_current_el(), but it is run-time
detection, so all EL code is linked, some of which might be unneeded.

This commit adds get_current_el_maybe_constant(). This is a static
inline function that returns a constant value if we know the exception
level at build-time. This is mostly the case.

if (get_current_el_maybe_constant() == 1) {
/* do something for EL1 */
} else if (get_current_el_maybe_constant() == 3) {
/* do something for EL3 */
}

If get_current_el_maybe_constant() is build-time constant, the compiler
will optimize out the unreachable code.

If such code is included from the library code, it is not built-time
constant. In this case, it falls back to get_current_el(), so it still
works.

Change-Id: Idb03c20342a5b5173fe2d6b40e1fac7998675ad3
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>