RFR(S): 7147740: add assertions to check stack alignment on VM entry from generated code (x64)

[Roland Westrelin]

> Why did you put the assert under #ifdef AMD64? You have current_stack_pointer defined for 32bit.

It's under #ifdef AMD64 on all platforms. Is your question about windows or all platforms?
StackAlignmentInBytes is always 16 but on 32 bit the stack alignment is not 16 bytes so the assert would fire even when things are ok. Also it's much less likely that stack alignment is a problem on 32 bit except maybe with recent version of gcc for which the stack alignment has apparently become 16 bytes.

Roland.