The padding alignment is not always calculated correctly in the foreign test case test/jdk/java/foreign/CallGeneratorHelper.java https://github.com/openjdk/jdk/blob/a74ebd048ae569296619c112c23169c46b571863/test/jdk/java/foreign/CallGeneratorHelper.java#L157
Using % alone is not correct. It needs to be:
     padding = alignment - (offset % alignment)
and apply only when padding != alignment.