[WebAssembly] Switch varags calling convention to use a register
Instead of passing varargs directly on the user stack, allocate a buffer in
the caller's stack frame and pass a pointer to it. This simplifies the C
ABI (e.g. non-C callers of C functions do not need to use C's user stack if
they have their own mechanism) and allows further optimizations in the future
(e.g. fewer functions may need to use the stack).
Differential Revision: http://reviews.llvm.org/D17048
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@260421 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed