Hello!
Sure, in i386/darwin.h we have:
/* Since we'll never want a stack boundary less aligned than 128 bits
we need the extra work here otherwise bits of gcc get very grumpy
when we ask for lower alignment. We could just reject values less
than 128 bits for Darwin, but it's easier to up the alignment if
it's below the minimum. */
#undef PREFERRED_STACK_BOUNDARY
#define PREFERRED_STACK_BOUNDARY \
MAX (STACK_BOUNDARY, ix86_preferred_stack_boundary)
This selects the maximal alignment to be 128 (16-bytes), the
testcase works for all alignments of 16-bytes or less. For more
aligning, I think that MAX, should be just a MIN:
Er, no.
MAX(X,Y) macro selects the higher of two values, i.e.:
#define MIN(X,Y) ((X) < (Y) ? (X) : (Y))
#define MAX(X,Y) ((X) > (Y) ? (X) : (Y))
(The definition is in system.h).
So, we never go below 128.